It seems that installing NextCloud & checking "Launch on startup" within the app settings doesn't work - also, I can't add it to startup items because there's nothing in /usr/bin called NextCloud or anything else I can recognize.
What, if anything, am I missing...?
Do You use the APT Package or Flatpak Version?
When nextcloud is shown in your startmenu, you can rightclick on the startmenu button>edit menu and search for nextcloud. Then click on properties and copy the command of the launcher.
Then open startapplications and create a new launcher named nextcloud there and paste the command.
Wow, that is NOT intuitive...but it worked, so thank you - I should probably bookmark this post, because I will absolutely forget next time I need to to this 