"offline" vaultwarden container


I would like to install vaultwarden on my qnap TS230.
I found some manuals how to do but all of the manuals make the docker/container station accessable from internet with a sub domain.

Is there a way to install vaultwarden without this?
I want only access “offline” when I’m at home.

I think if I’m not at home I can open bitwarden app (my vault) on Android or IOS without having physical access. In case that I add a new entry it will sync automatically if I start the biwarden app at home?
Or I’m wrong?

It would be great if someone can help a little bit.

Maybe some English manuals not so easy to understand for someone who English is not the native language.

Thanks in advance

Check this post

Regarding this section specifically,

This would not work as you expected. Bitwarden will not allow you to save offline, though you can read-only with the local cache.
I would recommend using a personal VPN to connect back to your house if you want that option, which imo works for a good balance of security and convenience.