Cannot even upload custom plugins

Found a plugin on the official marketplace. Can’t install it in the in-app market place because that one lists only about 10 plugins
So I wanted to upload it. Says “Enable upload in config file”
Did that, reloaded with mmctl config reload and then sudo systemctl restart mattermost

Did add MM_PLUGINSETTINGS_ENABLE=True to the env file, instead, repeat the same reload and restart. Nothing.

The link in the in-app screen Enable plugin uploads in config.json. See documentation to learn more. leads to
Not useful (exceptional: the link is at least not broken, as so many other links inside the app)