Your post suggests to me you are best served by an old Thinkpad. It has your best chance of running niche OS such as Haiku, BSD, 9Front, GNU/Hurd, GNU/Linux out of the box, more so than Framework whose features are not yet supported by all free OS.
More importantly it is a low cost way to see if an open source OS suits yourself without being left with an expensive machine gathering dust if it does not work out. You can switch to Framework if you succeed with transition. What are you migrating from?
As for the recommended OS, why not try Haiku which is making leaps and bounds as a user friendly OS?