Since (apparently and approximately) 11 days ago, the prescribed
  cvs -d anoncvs@mandoc.bsd.lv:/cvs co mandoc
invocation dies for me with
  cvs [checkout aborted]: end of file from server (consult above messages if any)
both on CI (https://builds.sr.ht/~nabijaczleweli/job/999999) and locally.

The CVSweb links (all pointing below http://mandoc.bsd.lv/cgi-bin/cvsweb/) say
  500 Internal Server Error
  OpenBSD httpd
as well.

наб