The simplest way of doing this would be to export your bitwarden vault in plaintext (as a json or csv) and then store it as a password protected zip file. This

The simplest way of doing this would be to export your bitwarden vault in plaintext (as a json or csv) and then store it as a password protected zip file. This should be easy to encrypt and decrypt on all operating systems, and would make it easy to move your vault to a new password manager.