I'm having difficulty installing the Adafruit AVR boards bootloader, under preferences i have the following URL listed in aditional Boards manager.
However when i'm in board manager the" Adafruit AVR boards" isn't available for me to install, the closest thing to it is the Arduino AVR boards and i have that installed but it doesn't list the board i actually need which is the feather 32u4.
There are two problems here. The first is that you need to separate the URLs with commas, not semicolons. Where did you get the idea that they should be semicolons? This is the second time in a week that someone had this problem. I'm wondering if there is some bad documentation out there that needs to be corrected so that others don't have this problem.
The second is that you have 4 different Adafruit URLs, two of which are duplicates and one of which is a link to the Arduino software page! That's bound to cause you problems. Just use the one URL as instructed by Adafruit (https://learn.adafruit.com/add-boards-arduino-v164/setup):