GNU/Linux Mint 20 GNOME Sushi 3.38 Source Installation Guide
How to Install GNOME Sushi 3.38 from Source Code and so Add QuickLook macOS Style to the GNOME Nautilus File Manager on GNU/Linux Mint 20.x Ulyana/Ulyssa/Uma/Una LTS desktop – Step by step Tutorial.
And Gnome Sushi for Mint 20 is a quick previewer for Nautilus, the GNOME desktop File Manager.
Especially relevant: the gnome-sushi 3.34 previewer is Not Working on GNOME 3.36+ and so currently the Source setup is the only available Solution.
Finally, this guide includes detailed instructions on Getting Started with GNOME Sushi File QuickLook on Mint.

1. Terminal QuickStart
How to QuickStart with Command Line on Mint
First, Update the Apt Repo Sources with:
sudo apt update
Contents