Pretty much all open hardware devices should be on such a list, e.g.
- NitroKey for both authentication tokens and storage (of e.g ssh keys)
- PGB-1 (based on RP2040) or Haxophone (based on RPi Zero) for music
- Precursor for token and dev (via its own FPGA)
so check CrowdSupply for more of such things.
I'd also add reMarkable. Sure you can use their cloud but you do NOT have to. It means you have your own Linux e-reader but also sketchpad entirely offline. You can work and sync with ssh or rsync and even setup your own cloud, cf https://github.com/ddvk/rmfakecloud . If you want something more open from the start check the PineNote but it's harder to get and you have to tinker a bit more.
FWIW before whine about the lack of editing or digitization : take of photo of the result on your phone, auto-upload to your desktop or even server and voila, a proper process to have your cake and eat it too.
I very often take a basic A4 piece of paper, or even a napkin, whatever is around really, then sketch to summarize a complex situation, snap a pic and send it to myself. Amazing way to think, very flexible and intuitive, at basically no cost and entirely private. Sure you still have to re-draw it after, IF you want to, but typically the idea itself is already on a substrate, maybe that's enough. If you want to edit it... guess what, you can edit the photo itself, no need to vectorize it first. Paper is great.