Device on LAN http://ds1621:5000/#/signin comes up from bookmark to login box and Bitwarden\autofill says No matching logins. Username and Password are filled in. Does Bitwarden not accept this address?
Could you perhaps be using the Samsung Internet browser, or otherwise be on mobile?
Otherwise the below post may assist with your questions, I believe there have been some changes but the Host auto-fill option appears to continue to work for both the browser extension and mobile apps respectively.
My browser (Firefox) complains about it being insecure but I can fill it in manually and it works. Bitwarden will launch it but then does not see it to fill it in.
The simple answer here is to not use http://ds1621:5000 on my local network, which works but Bitwarden doesn’s see as a valid URL but to use http://192.168.1.122:5000 (it’s IP address) which Bitwarden does see and fills in. The question is and was why doesn’t Bitwarden see ds1621. LastPass did…but I don’t want to go there.