@abloo was having trouble with this myself and then found: https://wiki.postmarketos.org/wiki/Terminal_cheat_sheet#Man_pages
(assuming you're running sxmo on postmarketOS)
That's going to install a lot of -doc packages, but then man pages should work like normal. After that, I think you need to install the -doc package for everything you install if you want them.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko