This datapack changes your gamemode to adventure whenever you engage in combat - with entities or players. It prevents players from building and placing blocks while in combat.
Showcase: https://youtu.be/nLMmfn8FYzo?si=wQfN77QdOheCDEwJ
(Note that it's the first version of the datapack on the video, the updated 0.3 arleady has more features and a bugfix)
Should be compatibile with most of the mods, tested with epic fight. *By default, it lasts for 8 seconds from taking damage. If you want to tweak it, go to data/immersive_combat/functions/start_combat and edit the value at the end of the 4th line. It's in ticks, so it's divided by 20 to get seconds. That's why default 160 results in 8 second.