Will the client side be open source? I hope so because I'm on FreeBSD so you probably won't make a compiled version :)
But perhaps you could do the monetisation via the sync service only and make the app open source :) That would be great, at least for me so I could compile it on FreeBSD. Some others do this, like Obsidian, for which there's an actual BSD port. But it's electron, sadly. But I understand... It's a tiny niche. I'll keep looking.
Of course I can't use flatpak and snap. And I can't stand snaps so no way I'd use that. Flatpaks are a bit better but not working on BSD.
I really used to love tomboy. It was fast, rich text, would automatically hyperlink notes together as you typed, it was so great. But they stopped development on it. There were a few reboots but they were complete rewrites and lacked all the speed and smoothness I loved.
Plume seems very pretty - good job on that, but....
"All notes in Plume are simple plaintext strings under the hood. Right now, all these plaintext strings are stored in a SQLite database locally on your computer. But we have plans to remove the reliance on a custom database and to store all notes as simple .txt files inside a folder."
I've been burned too many times by organizational tools that like to keep your notes internally stored within their systems.