The problem is that when someone with the Enderian Origin tries to drink from a water bottle, they get damaged, which is a bit counter-productive. Also, Merlins shouldn't really have to drink water as they're already constantly underwater. Can there be an exception to disable dehydration for players who choose such origins? Thanks in advance :)

Yes, there is a command for making players have dehydration :)

Oh! Well, is there a way modpack devs can run that command automatically for when players choose that origin? Also, did you mean "for making players NOT have dehydration"? thanks

That is a good question, I don't know.

is there a way modpack devs can run that command automatically for when players choose that origin?

basically globox would have to add a config option specifically for blacklisting specific origins from having dehydration so modpack devs could adjust it, otherwise players or admins will just have to handle it case by case
assumedly

There is already compatibility with https://github.com/Globox1997/Dehydration/blob/1.18/src/main/java/net/dehydration/mixin/compat/PlayerOriginComponentMixin.java

With the command callback https://origins.readthedocs.io/en/latest/types/power_types/action_on_callback/ you can set the players hydration with /thirst playername false