Yes! Fenrir works on Saturn's from any region, or Saturn's modified with a region-free bios, (switchless) region-free mods and 50/60Hz mods.
If you have a region switch, you can set the console's region to the one you prefer, but you need to also set Fenrir to the same region in its settings. Fenrir's setting needs to always match your console's region, but you only need to do this once, or whenever you manually change your console's region.
If you have a 50/60Hz mod (highly recommended) you should set the speed to the appropriate speed needed by the game. i.e. PAL games need 50Hz, while NTSC games need 60Hz.