We’d really like to get Perfmatters, which is 100% GPL here. We spent an entire year comparing the downloads here with those directly from devs and we know you are dedicated to good hygiene. We can’t say that for others and simply don’t have the time to carefully research and evaluate others.
We haven’t used the plugin and can’t be sure that it will work without modification and without the license key but this page says that without a valid license you won’t get updates, not that the plugin will not work: https://perfmatters.io/docs/how-to-install-perfmatters/
We’d be glad to add a donation $19.95 if that will help.