Notion doesn't use OT. Most things are last-write-wins, but we have operations that merge like list re-ordering or permission changes. Today our text is last-write-wins, but we're developing a CRDT solution – if that sounds like something you'd like to work on, shoot me an email jake@makenotion.com or apply https://boards.greenhouse.io/notion/jobs/5602426003
I believe Figma, Notion, Google Docs, etc all use some form of OTs which aren't necessarily a perfect CRDT