DebugPoint published a tutorial about upgrading to Linux Mint 20 from Linux Mint 19.3.

How to Upgrade to Linux Mint 20 from Linux Mint 19.3

If you are running Linux Mint 19.3 “Tara”, here are the steps you need to perform to upgrade to the latest Linux Mint 20. Before you perform upgrade, remember the followings: You can only upgrade from Linux Mint 19.3 64-bit version to Linux Mint 20. The following upgrade process will not work for Linux Mint

How to Upgrade to Linux Mint 20 from Linux Mint 19.3