Something small and 2 or 4 GB RAM. Raspberry pi's compute power is good enough for me, I'm not doing anything too intensive.
Is raspberry pi 4 still the best answer?
I am a tinkerer and don't mind tinkering. I typically use Gentoo Linux as main OS. I also don't mind ARM or other architectures. I've been eyeing the RockPro64 as well.
A low end celeron NUC would be best. I have one that has been doing the heavy lifting for my home services for 4 years