MySQL open_files_limit - cannot change this variable
I needed to edit /usr/lib/systemd/system/mysqld.service and add

LimitNOFILE=infinity
LimitMEMLOCK=infinity


Then run systemctl daemon-reload and systemctl restart  mysql.service.

Now the variable is capped at 65536 for some reason unknown, but I can live with that for now.

Found this at https://unix.stackexchange.com/questions/152186/mysql-max-open-files-more-than-1024#answer-157910