lang/mono and lang/mono5.10 are the same ports. One of them should be removed.
via ports r558399 ... > Repo-copy existing lang/mono port to lang/mono5.10 in preparation for > switching lang/mono to a metaport. This appears intended
I know, this is why I CC'd linimon. Still, it's been stalled that way for several months. linimon probably wanted lang/mono to switch to newer version (e.g. lang/mono5.20), but somehow dropped the effort. So currently lang/mono5.10 should probably be removed.
Unfortunately I burned out while trying to work on this project (among other things). Release this PR.
*** This bug has been marked as a duplicate of bug 251795 ***