There is definitely schematics out there for older linear BJT and MOSFET PSU's, that are probably pretty good. The main thing is just to spend the money on the actual transformer and hardware.
I salvaged a few transformers from 50/100W stereo's, overall they have not been very useful for me trying to make a variable PSU. I should lower the ratings, and then they would be ok. I did use the biggest 1 to make a 0-20V 1A PSU, and it basically works, but I didn't buy the real hardware for it yet, so I haven't built a proper case with plugs, etc.
IDK, I have a few transformers from old TVs and stereo's, I just really expected they would be a lot more useful, but I should aim lower, like 10V 0.5A. Or in fact just recyclye them and buy a better trans. for another linear PSU. The I would copy some old design.