Maybe try programming? It’s incredibly exciting once you get the hang of it. It can be frustrating at times but it’s really rewarding. Since becoming my hobby/job its given me an endless source of things to do at home. Plus it can open up new career paths :)
I suppose the most tangible benefit I get out of it is embedding a custom initramfs into the kernel and using it as an EFI stub. And I usually disable module loading and compile in everything I need, which feels cleaner. Also I make sure to tune the settings for my CPU and GPU, enable various virtualization options, and force SELinux to always remain active, among other things.