im mining on manjaro right now with a 5700 while im typing to u
all u have to do is install manjaro then add opencl in add/remove software
then i use corectrl, prolly have to add this, to underclock and undervolt as well as fan curves
then im using teamredminer

at most u might have to update the GRUB to fully unlock clocks and fan curve
just search for "overclocking amd linux" and u should find multiple detailed instructions to update GRUB