nobody here, but Discord's way more popular than mumble, i have yet to heard of any gaming community that uses mumble actively other than TF2 pro scene honestly, if you want reach and new players going for the most popular option would be the ideal which is Discord atm, quality wise discord's exactly the same as mumble.
IMO people should get used to use invoice chat anyway, look at CS:GO for example. ingame voice should be obligatory at risk of getting reported