I was part of a project that helped bring a usable Linux distribution on this line of palmtops -- JLime (you can find references on the net, but the main site has since gone dark). This includes the 620LX, 660LX, 680 and 690 (based on SH-3 processors), as well as the 710 and 720 (based on ARM processors).

I personally had the 690, which was suprisingly usable (and probably still is), even with its 133MHz CPU and 32MB of RAM. Finding and porting software was, even in ~2006, especially hard, given the hardware constraints and unique screen aspect ratio (640x240 resolution).

I still have the page for the distribution up here[0], and a software repository set up here[1], in case the author (if they see this) or anyone else that has any of these machines stashed away is feeling adventurous...

[0]: https://deuill.org/code/jlime-vargtass/ [1]: https://repository.deuill.org/hp6xx/vargtass/