I have also followed all of the other recommendations outlined on the Macports webpage for the same issue ... to no avail once I start running "sudo port install ..." commands.
M1 Macbook Pro; OS 11.2.1; Macports v2.6.4. I run from my general account as a sudoer. I have downloaded the Xcode 12.4 command line tools from Apple Developer, and have run the recommended licence activation commands as privileged user. I still get the warning ... Greg./
