This mod is marked as server-side only on modrinth but modpacks do not work without it being installed on the client. At least the version for 1.20.1 is affected.

That is the case for most modpacks, but it depends on which mods use Cardinal Components API. There are mods which use CCA while being serverside only.

Ah I see, it was marked as unsupported clientside, but it should be optional instead. Should be good now.

This is currently listed as "Supported environments: Server-side" only. Seems to be a regression caused when Modrinth changed their tagging system? This should probably be marked as supporting both sides.