Well, there are vintage resources and there are modern ones.
For vintage ideas, not to mention techniques and information, peruse the phenomenal
stacks of (searchable) PDF resources at https://worldradiohistory.com/
Check, e.g., the "Sams" books at that site for ideas and information. There are also DIY oriented (vintage) publications such as Radio Electronics
and Popular Electronics --
some UK and European equivalents, too.
I don't know what it's like today but audioXpress
magazine used to be an excellent resource for projects and ideas.
Modern DIY has largely devolved into "buy some modules, wire them together, and stick them in a case" -- which is OK but not nearly as interesting nor informative as starting with a bag of parts, some wire, and building from scratch.
Vacuum tube DIY is way
easier (not to mention more forgiving) than solid state -- but there is (in most cases) the potential (no pun intended!) hazard associated with high voltages. Nothing that some common sense (and a little pre-education) cannot render a very acceptable risk, but I recognize it is a disincentive to some folks.
There are some interesting low-voltage vacuum tube designs, such as Pete Millett's hybrid headphone amp using late 1950s "space charge" tubes (low plate voltages, developed for automobile radio use before high frequency transistors were very practical/affordable). Pete's got lots of interesting projects, as does Nelson Pass.
Finally, the OP might want to start with a kit, where the parts have been selected, some of the grunt work (chassis fabrication) may be
done already, and instructions provided. It could be a good way to ease into DIY. ]
Loudspeakers are a pretty good option, too, if the OP has woodworking interest/skill and access to the necessary tools. Still some safe and easy electronic work to do in crossover fabrication (and/or design), so not just a carpentry exercise for a traditional passive loudspeaker.
more to come anon
A Pete Millett hybrid headphone amp I built for a charity auction a while ago...
(the blue light is entirely for effect --
although I did use a blue LED pilot light