Great plug in, top solution for the servers I manage for my son and his friends and there you tube channels.
It's a pity it won't work as the connection with mysql fails, necessary for the multi server setup.

link to the logfile:
https://pastebin.com/B52tvLhj

~# java -version
openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment (build 14.0.2+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 14.0.2+12-Ubuntu-120.04, mixed mode, sharing)

MySQL version 8.0.23-0ubuntu0.20.04.1

I found the problem I think, there's a conflict with another plug in
https://www.spigotmc.org/resources/friends-premium-mc1-8-1-16-party-system-and-gui-for-bungee-and-redis.86504/

Solved by the dev of the friends plug in