Posted this on bsky but I see you're taking a break from there.

This won’t help with the number of devices, but the Supernote Nomad may be worth investigating as a dedicated digital notebook which could also serve as an e-reader (with access to Kindle for your current books to boot). I bought one in January and have been extremely happy with it. It has an excellent feature set for note-taking, and is distraction free outside of notebooks and e-reader functionality. It has online sync but stays offline unless actively syncing. It's also a great size, the same width as the Kindle Oasis, but about an inch taller.

Also, it's super forward-thinking in its design. User-replaceable everything.