Hello,
I don’t know how Bitwarden works, but if you can use it perfectly locally. You can try to disable NLA and have a try.
This will make authentication happen on server side.
a. Open gpedit.msc applet.
b. Navigate to Computer Configuration -> Administrative Templates -> Windows Components -> Remote Desktop Services -> Remote Desktop Session Host -> Security.
c. Enable Require use of specific security layer for remote (RDP) connections and select RDP as Security Layer.
d. Disable Require user authentication for remote connections by using Network Level Authentication policy.
Reboot Terminal server.
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