Mini PC/PC with a script to run gamescope -fe -- steam
on boot is as close as you'll get atm. That will run Steam in fullscreen embedded mode.
I have a PC all set up for it but there is a bug with 10xx series NVIDIA cards that causes the screen to go black when the cursor is hidden. Very upsetting. Need to throw an AMD card in there.
I was using Joplin for a while... Self hosted their server. On two occasions it screwed up on me and wouldn't load my folders... Luckily I had backups but it was still frustrating. I don't recommend them purely because the notes are stored in a custom format instead of just plain text files.
My favorite way of doing notes now is with git, currently using a free private repo on gitlab.
Just clone the repo on whatever PC I need them and it has backups and version control.
Then use GitJournal on my phone.
It's perfect for me. I love it.