I am going to be the odd man out on here when it comes to the "easiest way".
The OP stated he is using Mint 22. But Mint has three desktop environments (DE's) based on Ubuntu; which are Cinnamon, Mate and Xfce. The OP never mentioned which desktop environment the OP is using.
I have been using Mint (with Xfce) since January of 2014 when linux Pale Moon was publicly released. My linux Pale Moon has never been installed because if the OP is a non-technical person like myself, using the linux Terminal can be a royal PITA.
The easiest method I use to use Pale Moon in Mint is "not" having Pale Moon installed. It is always uninstalled and I NEVER have to use the Terminal to get Pale Moon to work. To make Pale Moon run with it being uninstalled, I use gui windows instead of the Terminal. But and there is always a "but", the method I use "will not work" in Cinnamon. It "will work" in Xfce.
I am going to guess the OP is using Cinnamon and if he likes Cinnamon and does not want to experiment further, then the OP can stop reading right here. But if the OP wants to try Xfce, then keep reading at my next paragraph.
If the OP is still looking at this post, click on the link below to see my last Desktop photo (with my pet cat, Tucker) of my Mint 22.1 (Xia) Xfce with the Panel displayed, which is located at the bottom of the photo showing all of my launcher icons on a regular basis I use in Mint. This will include the Pale Moon launcher icon which is located on the right side of the Panel. It will be to the left of the Firefox launcher icon.
download/file.php?id=19729&mode=view
The above is just "food for thought" because lots of users have a lot of trouble trying to get Pale Moon working by installing it in Mint by way of the Terminal. BTW, my method also works in MX Linux as well as Debian as long as I choose the Xfce DE in both of those two linux distros as well.
And as a final point, my method of not having Pale Moon installed and having it work while staying away from using the Terminal, as long as I stay with distros which offer the Xfce DE; it works with the distros I have experimented with and they are Linux Lite, Peppermint, Spiral Linux, Sparky Linux, Xubuntu and Manjaro as well.