DrJack60 I'll keep this thread updated with any findings but it seems to be slim pickins for FOSS handwritten note apps. I made the mistake of opening Notability (not FOSS) the other day to be met with a new UI overhaul that makes this all the more painful.
Such features like pen smoothing, selection color changing and pen width changing, and background grid customization are extremely crucial to me. Perhaps I am too picky to be gunning for FOSS only on this one. I'm sure the security of GrapheneOS sandboxing on the Pixel Tablet could still be sufficient for some Google Play notes apps.