I have tried to change the default email client to thunderbird. I did so via systemsetting --> applications --> default applications. I put in there "thunderbird" as the default email client. Unfortunately the default seems not to have changed because every application which uses mailto is poping up kmail client and not thunderbird.
Any suggestions how to solve this? Is there a commanline way to change the default email client?
I am working on ubuntu 18.04 with Kde Plasma 5.12.5