All athletes competing in France, without exception, are required to hold a** valid Triathlon License**: 
If you have a valid annual triathlon license from France, Great Britain, Germany, Belgium, Luxembourg, Switzerland, Spain, Italy, Portugal, or the Netherlands, you only need to provide us proof of your annual license.   If you have a valid annual triathlon license from another country not listed above, you must additionally purchase a One-Day License from the French Federation.  If you do not hold an annual triathlon license, you must purchase a One-Day License from the French Federation AND provide a valid medical certificate.  
I did it for AdH triathlon. It’s pretty much a requirement for all endurance races in France.
Went to my doctor and paid $30 for a letter that I probably could have just faked in MS Word. It’s not like they’re going to call Canada and verify it.
So I listed my USAT membership and one-day French License and it’s showing me as validated.
I have the form, but it’s not showing me as needing it now, so I think I’ll carry it to the race but not worry about listing since it’s not needed as stated above.
I’ve had to provide a medical certificate multiple times for a trail ultra in France. My primary care doc has signed it every year without question after my annual plan-covered physical, which is very basic. He’s been my primary care doc for more than a decade so he is familiar with my health status and my endurance sports endeavors. The certificate for the race requires that the doctor stamp the certificate, so I’ve had to educate the RD that M.D.s in the U.S. don’t have stamps. I’ve had the doc include his medical license no. with his signature and I provide a print from the state medical board website that verifies that is license is valid.
You can download a form on the Ironman website and get the doc to sign that after the medical. I had one done here in Italy before entering Challenge Frejus in France. Challenge also had the link to the French website where you download their form too. It was very easy. If your doc knows you they won’t need to do much of a medical, there is an official written declaration for them to sign.
When I lived in France, these are pretty easy to get/signed/etc…
However, for those outside of France, depending on the country - they can be a proper pain in the ass to get done. But ultimately, you’ll need to upload one to the Ironman portal to get approved.
For AIX 70.3 back in May, I used a UK company that did it. I filled out some stuff online with some medical history, and got a proper sports medical certificate for France later that night. Ironically I’m pretty sure I found the link here on ST from a previous thread. I did some lazy research and found a few other people that seemed to say it wasn’t a scam, and I cross-referenced the doctor that actually signed mine with some online sleuthing. Either way, the end resultant was a legit medical ceriticate. Frankly, having lived in France - the amount of work they did was no different than many French doctors signging off too (or, at least my doctor).
All athletes competing in France, without exception, are required to hold a** valid Triathlon License**: 
If you have a valid annual triathlon license from France, Great Britain, Germany, Belgium, Luxembourg, Switzerland, Spain, Italy, Portugal, or the Netherlands, you only need to provide us proof of your annual license.   If you have a valid annual triathlon license from another country not listed above, you must additionally purchase a One-Day License from the French Federation.  If you do not hold an annual triathlon license, you must purchase a One-Day License from the French Federation AND provide a valid medical certificate.  
So based on the 3 bullet points you listed, if from the USA and only hold a USAT license, one must purchase a one day French License. That one day French license seems pretty pricey.
When I did 70.3 Aix last year we had to have the medical certificate uploaded on some website (“dokeop”) and then wait for a validation email. There is a deadline to have this done before the race. Don’t underestimate the French’s obsession with paperwork and having absolutely everything in proper order. Maybe it was just the covid stuff still going on but I was flabbrgasted by how much red tape there was to deal with just. Be prepared.
All athletes competing in France, without exception, are required to hold a** valid Triathlon License**: 
If you have a valid annual triathlon license from France, Great Britain, Germany, Belgium, Luxembourg, Switzerland, Spain, Italy, Portugal, or the Netherlands, you only need to provide us proof of your annual license.   If you have a valid annual triathlon license from another country not listed above, you must additionally purchase a One-Day License from the French Federation.  If you do not hold an annual triathlon license, you must purchase a One-Day License from the French Federation AND provide a valid medical certificate.  
So based on the 3 bullet points you listed, if from the USA and only hold a USAT license, one must purchase a one day French License. That one day French license seems pretty pricey.
Yes. I don’t think that’s optional, ie I don’t think you can not purchase the day licence if you have a medical cert. You just don’t need a medical cert if you also have a USAT licence.
I got one for $20 https://medicalcertificate.in/. They ask you for a screenshot of your bpm and blood pressure and video of you walking. Make sure to ask them to add the exact words they require, something like “competition in triathlon”.
Are you sure? I purchased my French 1-day license and provided my USAT license and DOKEOP is showing me as fully registered and not requesting any additional documention (like the medical certificate).
Too add some additional clartiy: DOKEOP shows my registartiong as “Validated”, which per the email from DOKEOP and Ironman confirms that “all of my documents are approved and I have nothing more to do on the platform”
Are you sure? I purchased my French 1-day license and provided my USAT license and DOKEOP is showing me as fully registered and not requesting any additional documention (like the medical certificate).
Too add some additional clartiy: DOKEOP shows my registartiong as “Validated”, which per the email from DOKEOP and Ironman confirms that “all of my documents are approved and I have nothing more to do on the platform”
I just did Nice. I definitely uploaded a note from my doc, but I can get one very easily so wasn’t a big deal. USAT does not work by itself, it may with the french license I can’t remember.
Are you sure? I purchased my French 1-day license and provided my USAT license and DOKEOP is showing me as fully registered and not requesting any additional documention (like the medical certificate).
Too add some additional clartiy: DOKEOP shows my registartiong as “Validated”, which per the email from DOKEOP and Ironman confirms that “all of my documents are approved and I have nothing more to do on the platform”
I just did Nice. I definitely uploaded a note from my doc, but I can get one very easily so wasn’t a big deal. USAT does not work by itself, it may with the french license I can’t remember.
USAT membership plus the French day licence should work. Of course if you also upload a medical cert they will accept it too, but you shouldn’t need it.