Never rely on any cloud service! A good cloud based password manager is end to end encrypted meaning the password manager provider cannot access your passwords and they are secured from the provider and any compromise of the provider. But you do not only need confidentiality but also reliability. The cloud is just someone else's computer that you store your data on. They can cease their service or stop providing you access to it at any time. Always have a local backup of anything important saved in a cloud.
With Bitwarden for example you can export your vault as unencrypted json and csv format. Those are widely compatible and allow you to easily access and import your passwords.
Do not save your exported passwords unencrypted. I strongly recommend creating a dedicated VeraCrypt or LUKS container or similar and saving the export directly into that without saving it to disk unencrypted in the first place.
Note that shared organizations are not included in the standard vault export and need to be exported separately.
Edit: Someone mentioned that Bitwarden's export feature does not export attachments. So export them manually if you need to.
Was also going to suggest KeePass and syncthing, it's been working flawlessly for a long time. In case of conflicts, at least keepassxc allows you to easily merge databases.
I originally used Keepass, but then I managed to convince my wife to use a password manager and needed something more user friendly. I switched to LastPass until they started charging, now we're on Bitwarden
A good cloud based password manager is end to end encrypted
Presumably end-to-end encrypted. Do not trust any of them. There is no good cloud-based password manager.
My personal recommendations:
KeePass (and its numerous alternative clients). The password database is one single file which would never have to leave your local network (or even: computer).
Gopass (pass with modern addins). The password database is a folder of files which can optionally be version-controlled in a Git or Fossil repository. The default encryption is GnuPG, but it also supports age.
You can't prove that their server is running the exact same code. A self-hosted Bitwarden server might be reasonably secure, but as far as I can tell, Bitwarden('s server component) is not designed for single users.
Honestly, i applaud age for being very simple to use and less likely to screw up as a result, but i wouldn't rely on it for files as sensitive as a password database, its relatively new and hasn't been audited.
Only somewhat screwed. The client still has a local offline cache. So you don't immediately lose everything.
The cache is read-only though and doesn't contain attachments.
Also remember: the normal export function of bitwarden also "just" exports the database entries; not the file attachments.
If you are the BitWarden server admin, what do you see per user? Just a blob of data called "encrypted password database" or something, along with something like a last modified date and version number for syncing purposes?
Bitwarden is probably a lot safer if you self host (which I do). You do inherently lose some security by having a server that holds your encrypted password database, but my instance isn't exposed to the internet.
are you using the official bitwarden server or vaultwarden? been thinking about selfhosting it myself, but i would need to expose it to the internet, and i'm not really sure if i'm up to the task of properly securing it