The current behaviour of DiscordSRV's group synchronization makes it so that a secondary group is assigned to a user based on role sync. However, this is the opposite for the booster sync where it is the primary group that gets set. Is there a possibility for an option to have the primary group of a user be set for roles, just like booster sync, and have them reset to default if they lose the role?

I already did and it always sets secondary.

Nope. If it does you've configured LuckPerms wrong

GroupRoleSynchronizationPrimaryGroupOnly is on and LuckPerms is configured correctly.

Assuming you haven't changed the configuration for luckperms, that screenshot only shows that you haven't configured it correctly

If you're talking about the group weights and how LuckPerms determines a primary group, they're configured correctly. What I'm referring to is that default is still present. I would've expected that the option would've just set the parent to sub and overwrite default. DiscordSRV does it for boosters, just not for role sync.

Unless you can prove the Vault is infact returning the right group as the primary, this still stands as a issue that isn't with DiscordSRV.

How would you like me to do this? I don't have a plugin on hand that deals with Vault debugging, but I guess I could write one for this purpose.

use GroupRoleSynchronizationPrimaryGroupOnly & configure LP properly with weights or switchprimarygroup