Hexen >>> Heretic. Also the Mac requirement of macOS 12 is only what's officially supported; it actually works fine on older OS versions as I can confirm. I figured that would be the case since the demo was the same.

This post says the game was developed with GZDoom and can be run with it.

Nice to see this here - love these types of games.

Please work on bringing Selaco here too! Devs have said there previous submissions to GOG have been ignored.

Almost to 800 votes. Agreed.

Indeed, but a slightty modified one.
Maybe some effects would not be functional with other GzDoom versions or closer relatives. In fact looking into the development posts until the 2.0.0 versions saves turned incompatible some times. Also in this game the SoftPoly renderer crashes the game in my computer and I guess it should not be necessarily in that way in the last GZDoom version.

Anyways I am not sure about the proper steps to use other Gzdoom with this game. Just for testing

Greetings

For transparency's sake, the most important changes in HoN engine from GZDoom are:
• The ability to load cross-IWAD saved games (this allowed us to put demo and retail saved games on the same cloud on Steam)
• The gl_particles cvar is now forced to "2" ("smooth"). This allowed for better looking particle effects (like the serpent gas cloud, and the grenade smoke)

There are a few other under-the-hood changes but they do not impact the gameplay at all, they were mostly changes to features or additional features that this game actually does not use so they don't matter anyhow.

As for everything else the game should load just fine with a bare-bones copy of GZDoom.

Right up my street, wishlisted!