Are there modifications I can make on a Mac Pro 2012 so it can run macOS Catalina?
There is a macOS Catalina Patcher by @dosdude1 that is supposed to be compatible with Mac Pro 5,1. As of this moment, it is currently confirmed to working with Dev Preview 9 and Public Beta 8.

With modifications like this, there is always the risk of data loss or bricking, so make sure to have good backups and follow directions carefully.