Decent mobile app (more than happy to pay for this if it’s a one time fee)
Bonus for a OneNote / Evernote style Android widget. Being able to scroll through and quickly select from my most recent notes in the OneNote widget is really helpful.
WYSIWYG editor on mobile and desktop (why in God’s name does every Foss notes app insist I use a markdown language?) with bullet points, numbered lists, bold, italic, underline, strikethrough, and headings.
Checklists (as in, ability to add checkboxes to notes)
Ability to create an arbitrarily deep folder structure
Tags would be nice
Import from popular apps like OneNote, Evernote, or Joplin is basically essential at this point. A lot of us have way too fucking many notes to move by hand.