Work Around for failed launch on OSX Mojave(also pc launch issues)
So out of boredom I threw league on my macbook I use for work, And it was really tedious getting it to launch. But I have found a workaround for those who are struggling (I've seen a few threads saying they could not launch or patch on Mojave). Workaround is as follows for those who cannot load the launcher/patcher. This is current as of Mojave 10.14.6, LoL Patch 9.14b. (Although today 9.15 dropped and may have resolved it, but this issue was not described in patch notes, although post game banner for mac got mentioned)
You have to go to Lol in finder applications, then right click to bring up the dropdown. Select Show Package contents. Then navigate contents>lol>then open LeagueClient. This opens the game, not the launcher. It wont connect to a match so will run the launcher as normal. This let me patch and update the game. It was loading just fine after that. No in game issues either.
Secondly, on PC anytime I have left the client open and my computer sleeps I get the normal prompt saying I couldn't connect to the game, but I can't seem to relaunch. I've had to restart in order to fire it back up. A little annoying, but an easy fix.