FA5 won't be officially supported until, presumably, 4.4 or later.
https://invisioncommunity.com/forums/top...nt=2728273
IP.Board Support
Installing FontAwesome 5.0.3 on IPB
Submitted by 410, 20-03-2018, 01:49 PM, Thread ID: 80845
Thread Closed
RE: Installing FontAwesome 5.0.3 on IPB 25-04-2018, 12:43 AM #19
25-04-2018, 12:43 AM
#19