For a moment I felt that perhaps I should add clarification about how I'm not trying to dismiss the cloud solutions (as in the notorious Dropbox comment), but instead am attempting to provide one of the many libre setups to answer the parent question, but in the end didn't get around to it.
My time probably isn't as valuable as that of the many people here (about 5x less earnings on average in Latvia when compared to places like US), therefore it definitely makes sense for me to upskill myself in any way possible, especially if I get usable software out of it.
But if you take the container based approach, there is almost no administration to be done:
First, install Docker: https://docs.docker.com/engine/install/ubuntu/#installation-methods (about 10 minutes, varies by distro)
Personally, i use Docker Swarm, but that's just a few more init commands and Docker Compose works as well: https://docs.docker.com/compose/install/ (about 5 minutes)
Then, set up something like Caddy for a reverse proxy: https://hub.docker.com/_/caddy (probably 20 minutes)
And then, set up Nextcloud: https://hub.docker.com/_/nextcloud (probably 20 minutes)
Lastly, install KeePass from the previously mentioned links and put the password DB in the synced folder (probably 10 minutes)
Ngrok, DNS challenges etc. might be necessary depending on the setup, but are not usually required for most regular VPSes.
Backups and updates should also be taken care of, but full VPS backups are mostly standard and you can just bump the container tag every month.
As for the UI, i agree in principle, but not in this case. KeePass has good UI and I'd argue that you don't need a team of UI and UX developers to keep track of some usernames and passwords (and maybe certificate files).
Furthermore, I'd argue that most of the cloud offerings are actually problematic because not all of them let you download the data as files. In contrast, KeePass works with files (much like SQLite) and therefore, if you'd prefer to use SD cards or Samba or NFS or whatever instead of VPSes to somewhat decrease the attack surface, or simply use tools that you know, then you can do that. Want Syncthing instead of Nextcloud? Go ahead!
I'm putting emphasis on this because the line of thinking that we need web SaaS platforms for everything is dangerous - it makes you think that the problem is more complicated than it actually is. Whereas in reality some people probably get away with using password protected spreadsheets (don't do this). The problem is complicated only from a security perspective. That's it.
The cloud solutions excel at convenience and things like browser plugins and it's good that they're offering options for the less technically inclined folk, but they're far from the only option.