I have a folder called "TIL" (today I learned) and under that I have one folder for each technology/topic. Every time I learn or do something that I need to remember, I create a new markdown file in the relevant folder (or create a new folder). Most of this I publish to the internet, at https://TIL.secretGeek.net

To publish it all I have to do is push.

I have a private repo too for TIL's I don't/can't share (and all passwords go in a password manager)

At work we have have a custom in-house wiki that stores all of our shared internal notes.