@itsfoss I use Joplin[1] synchronized through my NextCloud instance.
Keeps my notes, reminders, to do's, even a check list for making sure I sort all 15 or so of my meds into my pill minder each weekend encrypted and easily accessible on each of my Linux machines, my GrapheneOS phone and iPhone.
And it integrates with biometric auth on my phones for an extra layer privacy & security. They have a solid hosted service for a modest fee but I self host for free.