PhpStorm on Linux - open "phpstorm://" links

I am using PhpStorm on Kubuntu 20.04 installed via Toolbox.  My framework generates phpstorm "links" like 

phpstorm://open?file=%2Fhome%2Fwww%project%2Fapp%2FModels%2FMyModel.php&line=494

so that I can directly open the phpstorm with the correct file and on the given line number. But how to make it work?

I was using https://github.com/sanduhrs/phpstorm-url-handler some time ago, but this doesn't work for me anymore, especially since Phpstorm is installed via toolbox.