Running Northgard
src/module.c(373) : FATAL ERROR : Failed to load library sdl.hdll

For anyone struggling, this above is a red herring.
Most likely a dependence library is not shipped with northgard.

$ cd *path_to_the_game*
$ file * | grep ELF | cut -d: -f1 | LD_LIBRARY_PATH=. xargs ldd | grep 'not found' | sort | uniq

will likely give you the culprits that you’ll need to install yourself.

had this error myself (trying to run northgard on fedora 40)
always the same error

searched for sdl.hdll
seems like the delivered is compiled for ubuntu and not fedora.

i downloaded https://github.com/HaxeFoundation/hashlink/releases/download/latest/hashlink-31cee2a-linux-amd64.tar.gz

and took the sdl.hdll from the archive and replaced it with the one in the game/ folder and it started.

hope it is also a solution for you