My self-hosted bitwarden server is only accessible from the LAN. Since the full password database is cached locally on each client, you can use it to lookup existing passwords just fine without a connection to the server. Bitwarden does require a connection to the server to add passwords, as it isn't a distributed architecture, so this setup does prevent you from adding new passwords while you are out and about, but I don't have the need to do that often, and in the rare occasions when I do, I write them on scrap paper in my wallet till I get home.