In this context “self host” can ironically mean using a cloud service for hosting. You can use a file based password manager and just sync the database. Solutions like KeePass have apps for many platforms, and they can often even directly load from cloud storage, like Google drive, OneDrive or DropBox. The password database is strongly encrypted, and even if your storage gets compromised, your passwords are still safe (assuming a good password or some then better security was used to encrypt it).

You give up the convenience of having a single service and having to get each device to access the file. But that’s it. It’s not that hard and so much better than a password service, even if just for their attack surface, or the “likely target” these are.