Oh that's cool! I tried to take part in their beta but it was a mix of the app wouldn't even start on my phone and when I finally found a version that would I couldn't find my invite key anymore. Guess it's time to give it a second chance :)
Professionally I love Logseq but I'd love to replace my personal Notion notes..
Mailbox.org is great, I like that you get caldav and carddav as well. They're very privacy conscious as well. It's true the recent price increase doesn't make me happy either. The service is great and I couldn't find a better deal so I stick with them. Except for the price everything is perfect imho