I'm in the same boat, and have more or less settled on simply writing plain text (markdown format) files in a plain directory structure maintained by me. I then use Obsidian to "organize" the notes.

I'm also guilty of just jotting quick notes into iOS Notes. It's always there, and "good enough" for most quick note taking tasks. I prefer plain text for longer notes (which i assume has a longer shelf life), but if i'm just jotting down a quick list of things i need to get done today, iOS notes is more than enough.