I have registered an .uk domain. As an Individual non-UK resident,
WHOIS info shows an error message Nominet was not able to match the registrant's name and/or address against a 3rd party source on 24-Aug-2023
Nominet passes your personal registrant information provided as part of your domain registration through multiple third party sources to ensure the validity of it. It appears that they couldn’t find your information (possibly due to you being a non-UK citizen), so it did not pass its automatic validation.
I wouldn’t be concerned about this message and it isn’t the first time I’ve seen it. If Nominet have reasons to believe that the information you’ve supplied it incorrect, they’ll reach out to confirm.