Download appprofiles and put files in /etc/ufw/applications.d,
git clone git@github.com:NathanTheGr8/UFW-Home-Server-Apps.git
sudo cp UFW-Home-Server-Apps/app-profiles/* /etc/ufw/applications.d
then tell ufw to reload the application definitions with
sudo ufw app update plexmediaserver
sudo ufw app info plexmediaserver
Use it with something like:
sudo ufw allow plexmediaserver