I think found a version independent approach for an internal display system without HUD plugins, so that's what I'm currently working on (it's already kinda working, but there's still a lot of code cleanup to do and some decisions to make, so it could take a bit for it to be released here)

Of course you'll be able to decide what you want to use with BetterHud still being the more viable option. MythicHud is really confusing, closed source without API documentation and it doesn't have as many Features as BetterHud, so MythicHud compatibility is no longer high on my to-do list. Instead, I'm working with the author of RealisticSurvival to establish an integration that doesn't require any extra pack on servers using it.

Anyway, to prepare for all of this, assembled resource packs now have their own output folder and the existing packaging process of BetterHud's assets to a usable resource pack has been updated to:
...fully support all versions from 1.21 upwards (no more red highlighted, outdated packs)
...make it a little more presentable by reworking the pack's description and adding sort of a gradient
...allow customizing the filenames of generated resource packs