Heavy Armor Master AND Barbarian Rage

[Hylomorph]

Excellent! If you can, let me know know in a few weeks if it worked as expected. If there are a handful of folks who are interested enough to use it, and it doesn't break for them, I'll clean it up a bit and repost it over in the Extensions forum.

[Ragnar Tryggvy]

This may or may not work for you. In my games, I use DR on armor and using an effects extension code the resist onto the armor itself. So just putting on say a set of chainmail armor gives the player a RESIST already. To make the Heavy Armor Master feat work properly with that, I created an item of armor called Heavy Armor Master [FEAT] that you add to your character sheet just like a normal armor. When you equip your heavy armor, you also equip this. It has the Effect coded in as follows:
RESIST: 3 all, critical, !magic, !psychic, !acid, !cold, !fire, !force, !lightning, !necrotic, !poison, !radiant, !thunder;
I have tested it a bit and that provided resistance to only slashing, piercing and bludgeoning damage and also applies to critical damage of that type as without adding the critical it would not subtract if the resistance exceeded the basic damage. Say you had RESIST: 2 all; from your armor and then the HAM resist. If a creature did 4 slashing, all would be resisted. If they crit and did 2 slashing + 2 slashing from the crit, the extra 2 would not be resisted without the 'critical' added to the RESIST code.
Not sure if this will help you, but it is working for me. Does require an equipment effects extension. The effects extension I use is https://www.fantasygrounds.com/forum...cs-characters), it is free and no, I didn't make it.
I hope this helps in some way, good luck and happy gaming.

[Hylomorph]

That's great! It's a trick I didn't think of: you can't combine "RESIST: 2 slashing" with "RESIST: slashing", but you can "combine RESIST: 2 all, !everythingbutslashing" with "RESIST: slashing". That approach is usable without the effects extension, too.

[Hylomorph]

If anyone other than me was crazy enough to use the addon code I provided back in 2020, it stopped working with a recent update to the 5E ruleset. Ragnar's post above provides a different way to accomplish the same thing, and that method still works.