This same update (KB5065426) stopped our machines RDCing to each other. Similarly, the issue was found to be that the machines had all been built and supplied to us with the same machine SSID. I found the easiest way to look up the machine SSID was in Powershell with the command "Get-LocalUser | Select-Object Name,SID" (without quotes and ignore the result from the last dash onwards).
Uninstalling KB5065426 and pausing updates has worked as an interim solution. We are evaluating the implications of using a SID-changing tool like SIDCHG to change the machine SIDs. I understand it has less implications than running sysprep /generalize which "resets a lot of things".
Good luck everyone!