KeepassXC at least allows you to export your passkeys should you choose. The people behind passkeys do not like this. https://github.com/keepassxreboot/keepassxc/issues/10407

Well, KeePass is self-hosted, and I hadn't heard of strongbox before, but it says on the website:

> Store your data anywhere you like, online or offline. Sync with every major cloud storage provider or your own server over WebDAV or SFTP. Use your Strongbox database with any KeePass compatible client on any platform.

I use nextcloud to sync my own keepass database across my devices. Both nextcloud and keepassxc are open source.

Please explain how self hosting open source software is locking me into a vendor.

If the sky falls and strongbox ceases working with mac/iOS I can use android and linux. Nobody is locking my lockbox.