Some tracкball-oriented communities that active today.
Forums:
https://deskthority.net/viewforum.php?f=3
Resource is mostly devoted to the mechanical keyboards, but some useful inofrmation about pointing devices is available. Currently unmoderated and flooded by spambots, but still operational.
https://old.reddit.com/r/Trackballs/
Probably, most populated place today, but unfortunately it suffers from serious flaw: many posts are filtered out. It looks like this: you see some tread with answers, but if opened - answers are not visible. Another "feature" is, the author of tread can delete it - so, your reply (perhaps with the information valuable for others) is just going to nowhere.
Discord channel:
https://discord.com/invite/hefvxTKffJ
https://www.cybertechhelp.com//showthread.php?t=227225
Really old trackball tread, but still active.
Reviews:
https://www.trackballmouse.org
http://xahlee.info/kbd/trackball_index.html
Manufacturers:
https://www.globalspec.com/suppliers/3868/trackballs
Collections:
http://www.phantom.sannata.ru/forum/index.php?t=17651
https://collectionerus.ru/collections/old-mice/
http://arvutimuuseum.ee/hardware/
http://www.kompjutry.cz/soubory/prislus ... _mysi.html
Japanese (read via Google translate):
https://kohzuka-trackball.netlify.app
https://twitter.com/kzktrackball
http://www.hykw.com/tbfan/gallery/index.shtml
http://mineko.fc2web.com/box/tb-room/items
https://twitter.com/nekotrackball
http://www013.upp.so-net.ne.jp/cyberdog ... ngton.html
https://www65.atwiki.jp/tbparanoia/pages/19.html
http://www1.plala.or.jp/sarahtt/nazo/24 ... zo-24.html
https://orz7.web.fc2.com/index.htm#sijiq1
https://www.mobile01.com/topicdetail.ph ... &t=1639308
https://watchmono.com/blog-entry-7107.html