Out of curiosity, why do you want to use a SIM card? Asking because I recently bought a Karoo 2 and not sure what functionality the SIM card would add.

It has something to do with the sim, it is related to the plan activated on that sim. The Karoo not working with a data only plan likely has more to do with the carrier and not the device. Telco's only want "non-phone" devices using data only plans/sims. If they don't know what a device is they are going to default to it being a phone and require a phone plan. I'll guess that the carriers have no idea what a Karoo is and it isn't whitelisted as a "data only" device (like a car or tablet would be.) It's possible that some carriers to recognize it. You could go fight with a carrier's customer service department to get it added as a data only device... but good luck with that.

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Team Zoot

Indeed I agree... curiosity doesn't kill a cat.

Just want to eliminate the headache of using my smartphone on the side of the road, want to condense functions on my handlebar.
I do what I call Urban touring cycling in & around city's.... Los Angeles, Paris, Tokyo, London, Chicago.... on nomadic trips of 5 to 20 days... area's to aera's, hotel's to hotel's.
Some kind of Triathlon's of discovery.

I among other things make maps with modern architecture POI.
I need the Sim to make it simple if for exemple I look for an hotel of anything unexpected requiring a rerouting.

Also I paid for that freak in function.... I want to use it..

Do you use a Karoo 2?

Okay wait have to go... barely had time to thoroughly read your post. I'll be back.

From the karoo2 website:

“Cellular - GSM (2G, 3G, 4G band coverage) 4G: Bands 2, 3, 5, 7;
3G: Bands 2, 5;
2G: EGSM900, DCS1800
Global 3G and LTE cellular band coverage available using a SIM card (SIM card not included)”

Here is a website that explains the bands used by US carriers
https://www.whistleout.com/...requencies-explained
Note that this website states that your device must be compatible with a carrier’s main band (denoted by an asterisk) to work — it looks like the only carrier that would work is T-mobile (on band 2). Although this advice is for phones - not sure if that is also true for the Karoo.