The best way to prepare for hills is to ride on hills. I think it's a pretty good way to prepare for the flat too!
However, I think a trainer can also be used to provide a heavily loaded pedal revolution which can't be achieved on the flat since inertia allows pedaling styles that are more problematic on climbs. Of course the trainer won't simulate the bike angle (unless you have a Climb accessory or something under the front wheel) or handling during fast descents.
If you have a 2km hill that rises 100m, that's 5%. Not very steep but steep enough and long enough to be reasonably useful. Also from what you say the gradient is comparable to sections of the race.
I'd consider doing some hill repeats on those if you think hill practice would be beneficial, it's not going to do any harm! It'll take you several minutes to get up those which is enough to start settling into a rhythm. Assuming you've already got a bit of bike fitness pacing on climbs is probably most important thing to get right.
I think most people who struggle with hills have one or more of three fundamental problems:

1. Inadequate fitness for steep climbs
2. Pacing
3. Inappropriate gearing

1. This unlikely to apply to anyone on ST. Even pretty modest fitness is sufficient to get you up a 20% slope so long as you have generously small gears and you're not very overweight. The limit occurs when you are going so slow that you can't keep your balance. Up until that point it's just about gearing.

2. This is a big one. I think lots of people who are unused to hills, feel like they're going too slow when they start climbing and start to push too hard and get the climb over with. Then they blow up before the top, or just fry their legs for later. You should put a little more effort in on the climbs and recover a bit on the descents as opposed to a constant effort for the whole ride, but the variation should be reasonably modest or it will become counterproductive. If I was cruising at 200W on the flat I might allow myself rise to say 230W on sustained climbs and 270W for very short steep ramps but that's about it. Pacing is probably the biggest single benefit of being familiar with climbing. A power meter or HR monitor are incredibly useful for this too!

3. Err on the side of excessive gear range. If you think a 25T is enough on the back but you're not sure, put on a 27, or 28T. If you think a 28T is sufficient but you're not sure, consider a 32T just in case. I did the Marmotte Des Alpes a couple of years ago and reckoned a 28T on the back would be sufficient but I wasn't sure. So I got a mid length derailleur cage to replace the short one and got a 32T. I'm not sure if I ever used it during the ride, I don't think so, but it was worth having and I've used it since. There's not much downside when you've got 11 sprockets to play with.

Thanks! Those are good pointers! Re the first one, I will try to get down to race weight a bit earlier in the season to avoid being depleted during final blocks, for running I have hit 68kg (187 cm tall) but for tri I am aiming for 70-71 kgs, but hopefully still not overweight!

In terms of pacing, I do have a PM, Powertap P1 pedals, but they have not been super reliable and I read that they are aero bricks. Would it be pointless to train with them on to get a "feel" for different watts uphill and then race with sleeker speedplays?

My god, gearing! I suck at thinking that out, always used the standard setup which came with the bike, I think it is a 11-25 rear/ 39-53 standard front. Will check out 28/32 rings!

Thanks again!

Gearing is pretty easy. It's very basic maths to understand it fully but you can simply increase the number of teeth on the largest rear sprocket (or decrease the smallest chainring at the front) to provide an easier gear.
Try riding up those local hills at your approximate planned effort. If your cadence is comfortable, especially if you still have another gear at your disposal, then you should be fine, assuming the race route has nothing steeper.
If your cadence is too low, it will be on that sort of gradient in the race too. Speed is determined by power, weight, wind resistence, rolling resistance and gradient, plus a few fairly negligible other factors. Cadence is determined solely by speed and gearing.

While training for IMWI with 4000m of elevation gain, I spent a lot of my workouts doing the insane mountains on Zwift since there is nothing remotely close to that in my neck of the woods.

Through trial/error, I found out a power zone I could do long sustained climbs with cadence, gearing, etc.

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Gone with the wind

Instagram: palmtreestriathlon

I have been primarily riding TrainerRoad's mid-volume half distance plans for a few years, and those have indirectly made me a very good climber. So, don't overthink it... if you are using a structured training plan that includes extended intervals decently above FTP, you will become a good climber. If you are training outdoors, then you need to incorporate those same kinds of intervals in your workouts-- don't just do miles, do miles with a purpose.

I raced this course a few years ago. Most of the elevation gain for the course is fairly mild climbing from Porta Pollensa to Lluc. This section can be done at fairly constant power output. I think I was running 50/34 compact with an 11-27. As others have mentioned, no need to overthink it. Work on building your threshold power back up.

Other places on the course there are some crazy punchy little climbs. I think it was the one in Muro where you turn 90° to the left and hit a climbing wall. I loved the big descent. The road is closed and you can use both lanes so it wasn't a problem at all. The end of the descent through Caimari is so cool. There were folks seated at cafe tables right next to the road while 3000 riders sped by them.

This is a fantastic course. It is the largest 70.3 field I've ever raced. Maybe 3000 with teams? The bike course can be crowded in places and you'll want to pick a good line in places like Muro. The team cyclists threw me off a bit as it was constant back and forth with few of them riding constant power.

If you can practice in the wind I'd recommend it. It blows all the time there that time of year and I'd say the wind from after the big descent back to T2 was a bigger impact than the climbs. The run course is so flat that you can probably afford to push the bike a bit. I probably overbiked and still set a PR HM at the time.

I've mentioned it before, but transition is huge and can be confusing. I was racked where the end of the rows were re-configured while we were riding. So when I came back in my row count was off and it took a looonnggg time to find my rack spot:(

There is no specific hill climbing fitness on the bike. Get strong. Get light. Gear properly. Pace properly.

The direction of force application does not change, as you are fixed to the bike. This is not the case in running, where the force application is markedly different when going up steep hills. Hills can help a lot with run training, but aren't really necessary to become a good climber on a bike.

Of course, somebody is about to call me an asshole and say I don't know what I am talking about and hills helped their FTP go from 150 to 500 or whatever. Hills can force riders who don't work hard, to work hard, in which case sure they can help, but this is not the magical hill fitness that many are searching for.

Same, I spent hours on TrainerRoad with their IM training program and the hours spent helped me be a better climber. Oh and I do a lot of squats on my free time too lol.

I noticed a couple of weeks ago that I suck on climbs and descents and wondered why: ok I train mostly on the flat.
I do not have lots of climbs in my neighbourhood so I went a weekend to the alps. Of course with the TT- bike.
It is different: you sit upright and use other muscles: also in your back. I must say it seems the weekend helped: It certainly did not become worse.

Important point: Before I could not hold my hands on the pads because of the U-shape of the pads. I could only climb with the hands on the basebar.
So I exchanged my pads with flatter pads and I can now comfortably climb more upright with my hands on the pads: big improvement.

Thanks for detailed race info! Sounds like the uphill part is pretty straight forward, perhaps should worry more about parts of the descent! Your account is inspiring, looking forward to the experience!

Did not know about teams participating, is that a big thing?

Re: the wind, I was thinking of running 808 front, fairly confident riding them, or is that too risky on this course?

Well sounds like an indoor program is the way to go. Fits pretty well with winter season (snow) looming too. May have to look into TR, read lots about their plans (including some where people bury themselves) but never tried it.

In the pst I did some really long trainer sessions (up to 6 hrs sprinkled with threshold efforts and standing max bursts) but have sort of lost the mindset for that, think that 2hrs would be my limit now. As a non climber riding outside would give some feel for how ’fast’ feels going uphill...

besides climbing and the advise above about gearing etc... Make sure you have good brakes and practice your downhill/cornering skills. There are some twisty descents coming off the climb where lots of people lose all the time gained storming up the hill imho.

I'd highly recommend doing a reconaissance ride to check out the bike course.
Its a nice bike ride. Run is dead flat as is the swim.

The advice above about presiding the descent is good. We were worried about it too and rode the climb to Lluc and then the descent. We had traffic and the descent was fine. Good braking is helpful as the switchback traverses are fairly long, but plenty of sight distance at corners and road is closed to traffic. After riding it we felt much better and it was a non issue on race day.

Maybe it is because I haven’t done a lot of races with teams. Or maybe because many races with teams start them early. But it was the constant back and forth with the team riders that took away focus. Head to head in tri bike legs I’m used to the field spreading out over the course based on speed. With these teams they would hammer, blow up, recover and come back through. More just an irritation that threw my pacing off at times.

I rode and 808 and would say it is fine for this course. The wind was constant and consistent not gusting. We spent the week after the race at a cycling camp and all our rides towards the north coast had similar wind conditions.

It is a great race and awesome cycling venue. You’ll enjoy for sure!.