For notes, I'm using #Nextcloud Notes to sync and work in the browser, with the NextCloud Notes Android app and the #GNOME app #Iotas in desktop.
Iotas doesn't save notes as .md files. Instead it uses a SQLite database but is great exporting notes as PDF, ODT, HTML and MD.
I'm still keeping #QOwnNotes in the mix, but I haven't yet set up the Nextcloud desktop app to sync with my Linux system.
#OneCalendar, Iotas and #Thunderbird sync with Nextcloud without requiring extra apps.
Today I synced my #Nextcloud #calendar with #Thunderbird. Just like with the #OneCalendar Android app, I generated an "app password" in Nextcloud at the bottom of `Settings -> Security`. Worked instantly.
Now I have a not-Google calendar in Thunderbird on the desktop and OneCalendar for mobile.
I'm not 100% happy with OneCalendar and will be shopping around for more mobile apps. OneCalendar seems to miss the ability to make an event repeat. Unless I'm missing it ...