How to set uploads space limit per user on Misskey?

Change the Policy of the role applied to the user. Since I have a single person instance, I just needed to update the default Policy Template from the Control Panel

1. Go to Control Panel
2. Click Roles
3. Either change the “Role Template” if you have no roles defined, or edit the role governing the users for whom the limit needs to be changed.

4. Their “Roles” page should show the new limit under driveCapacityMb and also their “Drive” page in Basic Settings