At work I've use a mix of physical and digital with a whiteboard to track my TODOs as I can always turn around to see what's next and I get a nice reminder at the start of my day of what I have to do. I also have a ~/.kb file, which is just a plain text file to store any scratch notes, commands, etc.

At home, I have a physical journal that I write in, and I hate to admit it but its kind of a mess, but I do have an agenda that I use to management appointments that is better organized only due to the virtue of the provided layout that it comes with.

I use Joplin with encrypted notes synced over Dropbox. I can use it on all my devices plus it has support for math and mermaid diagrams. I also use a Leuchtturm1917 120g notebook which is perfect for writing and sketching with a fountain pen.

I use single notepad.exe file in work. For private use I tried to use many apps, Obsidian got the closest but I couldn't make it stick.

At work: one big text file with Notepad++.

At home: Apple Notes.

vi .work/TODO (under SVN control on my server)

Stickies app on MacBook desktop

Pieces of scrap paper torn from physical envelopes etc!