Mouse cursor is different from the system-wide selected cursor. This is related to Snapcraft, and has been confirmed as of December 2020 and January 2021.
Ditto here! Ubuntu 20.08 with a brand new 4K monitor, TINY mouse cursor. Don’t even know where to start to try and fix it but might try and rummage around so I’m not just another user posting issues about open source software without trying to help!