Proposal to take ownership of this port and update significantly.
mono@ has basically been dead for over a year, and has not updated the lang/mono port. I have been working closely with upstream for about a year now, and we have made tremendous strides in improving FreeBSD support as well as making upstream more friendly to the ports architecture. I have also worked with them to integrate FreeBSD into the official Mono CI, and we have gotten to a point where nearly all tests are passing or the failure is itself a failure of the test.
At this point I believe we are ready to take the next step and start bringing lang/mono officially current, and I am comfortable enough with the intricacies to take ownership of this port. There will be additional changes needed over time due to changes in the upstream organizational structure; however, these will not affect this port.
Outstanding work currently is confirming successful builds on aarch64 and powerpc64; it is known to not compile under qemu due to an MCS crash.