I've created another Brisk logo change tutorial for Ubuntu MATE 20.04 LTS: using another theme's icon set (not just Adwaita).
Found here: https://gripfastistech.com/index.php/blog/94-how-to-change-the-brisk-menu-icon-in-ubuntu-mate-20-04.html
Hope it helps someone.
PS: My continued praise for this project and the Mutiny layout!