I self host vaultwarden and its great. Its an easy self host, and in my experience, it has never gone down on me.

That being said, my experience is anecdotal. If you do go the vaultwarden route, realize that your vault is still accessible on your devices (phone, whatever) even if your server goes down, or if you just lose network connectivity. They hold local (encrypted at rest) copies of your vault that are periodically updated.

Additionally, regardless of the route you take you should absolutely be practicing a good 3-2-1 backup strategy with your password vault, as with any other data you value.