I had an old iBook G4 that could be useful for an elderly person, to be able to do her banking and basic internet browsing without having to use an XP-vintage, molasses-slow, honeypot-aspiring PC. There's a reasonably complete and up-to-date guide in https://ricanlinux.blogspot.com/2015/03/ubuntu-mate-on-my-ibook-g4.html . I had to change a couple of details; and there are a couple of practical considerations to be had. (Note to self: "lightness" in Linux rather correlates to "barebones" [3] , which correlates with "hardcore" (text configs, mailing list scouring, lots of googling). Next time I'll be trying a heavy-weight distro for this kind of thing; better slow-but-useable than less-slow-but-WTF.)
Running away from the comfort zone