Usually the Ticwatch Pro 2018/2020 (catfish) is widely available since it was a popular model. The more recent version Ticwatch Pro 3 (rubyfish/rover) is freshly ported and not as well supported as the first Ticwatch Pro yet. I bought one new in box just this week from german ebay for 70€. We got a Team member in the US/ML who is hoarding watches and seems to have no problem acquiring them :D I wish you luck.

This sounds like an interesting investigatory problem you've put in front of me...

Thanks so much!

I can see some Fossil Gen 6's on eBay in the US. (I only learned about AsteroidOS today and I'm not in the US)

Did you consider PineTime?

While the PineTime/Infinitime is an awesome project everyone in our community roots for, the hardware platforms are totally different. The PineTime is microcontroller based and works on just 64KB memory and 512KB flash. AsteroidOS is a linux distro tailored for devices with SoC, half a gig of memory and >2GB storage. Arguably its much smarter on many levels to use the microcontroller approach for the rather simple smartwatch task. But somehow these full SoC general purpose computing smartwatches have been produced and we as linux people slipped into the niche of seizing those.