/usr/bin/mawk: mawk 1.3.3 Nov 1996, Copyright (C) Michael D. Brennan
This is the default mawk bundled in Ubuntu 18.04.
Ubuntu 20+ bundles /usr/bin/mawk: mawk 1.3.4 20200120, so we end up testing this version two times.
https://invisible-island.net/archives/mawk/