Self hosted Google Keep (and maybe Microsoft To Do) alternative with Android App?

hey

i'm trying to degoogle-fy (and the microsoft-ify) further - two app i'd like substitute are Google Keep and Microsoft To Do.

I can live without to do lists (or search a separate app for it), but a subsitute for Keep would help me a lot, as we use it often in our family

i first had a look at joplin, but as far as i understand, it's "just" an app and you'd need something like nextcloud to sync?

that's why i'm looking for a server-application that also has a companion app for android (otherwise i won't get spouse approval ;P )

if the app could also offer to do lists, similarily organiszed like MS To Do, it would be great - but that's not a must have

can you recommend a reliable server-application?