If you want a delightful hobby, then I can recommend building your own guitar pedals.
It combines music, electronics, general nerding out (e.g. debating germanium VS silicon diodes), and some visual design if you want to make the enclosures pretty. You might even be able to sell some.
I started by building a kit pedal with one of my kids as a weekend project.
Some search terms to get you started: build your own clone, diy pedal schematics, tag board music effects.
Modular synths are similar in that way, except way less popular so more expensive on both kits and ready-made stuff.
VCV rack - software: https://www.factmag.com/2017/09/12/vcv-rack-open-source-virt...
There's also Cardinal, which is essentially VCV Rack but provides free and open source plugins.