It looks like Fusion 360 runs fine on Linux these days, I don’t know how reliable that is in practice (I would expect not very much).

OnShape is a great option if the licensing terms are compatible with what you are doing. They used to have similar licensing terms as Fusion 360 where you could still get paid for your work with a free version (i.e. YouTube) but changed the terms to remove this loophole. Fusion still allows this with the Startup license but of course could change their mind at any time, then you’d be out of luck.

I dislike the lockdown of Fusion 360 but its mental model works with my own (I can’t “get” SolidWorks and never remember how to do anything). Speaking of SolidWorks, they added a reasonably-priced license for DIY/hobbyists, but it’s the same lockdown as Fusion 360 and still Windows only.

I’m in the same boat as you, just a hobbyist doing this for my own use, I have no interest in becoming an industrial engineer. For now I will keep using Fusion 360, and when that stops being an option I’ll move on to something else. I can whip out models for my prints easily enough and the 10 documents limit is just an annoyance, not a real limitation.

At the very least whatever you design in Fusion 360 or OnShape won’t be stuck in there, you can export it out via .step files. You lose design history (if applicable) but not the model itself.