The reMarkable cloud is crap and has been since the beginning. I wrote a free/libre offline management tool called reMarkable Connection Utility (RCU) that is decently popular, used by several thousand people. Beyond backup/restore of editable notebook data, it has a lot of unique features the manufacturer can't/won't support (like exporting with native PDF highlight annotations).
[1]: https://www.davisr.me/projects/rcu/