Sorry mime the second (mate-control-center vs. firefox)

Question

My OS is Debian stretch (mate Desktop) Since about 2 years I have a problem with default setting for application browser(in mate-control-center) and firefox. whenever I let firefox set itselfs as default browser in (about:preferences) my prefered application settings in mate-control-center changed from firefox-esr to thunderbird for default browser. And the other way around.

Both seemed somehow registert

 alex@Taomon:~$ gvfs-mime  --query x-scheme-handler/http 
    Default application for 'x-scheme-handler/http': firefox-esr.desktop
    Registered applications:
        thunderbird.desktop
        firefox-esr.desktop
    Recommended applications:
        thunderbird.desktop
        firefox-esr.desktop
    alex@Taomon:~$ 

---

alex@Taomon:~$ gio mime x-scheme-handler/https
Default application for 'x-scheme-handler/https': firefox-esr.desktop
Registered applications:
    thunderbird.desktop
    firefox-esr.desktop
Recommended applications:
    thunderbird.desktop
    firefox-esr.desktop
alex@Taomon:~$ 

How can I remove thunderbird as registered application for x-scheme-handler/http and x-scheme-handler/https. I hope then my Error will be gone for good.

edit

In ubuntu (focal) is only firefox registert.

alex@Guilmon:~$ gio mime x-scheme-handler/http
Default application for “x-scheme-handler/http”: firefox.desktop
Registered applications:
        firefox.desktop
Recommended applications:
        firefox.desktop
alex@Guilmon:~$ 

there is also thunderbird as e-mail client installed.

Answer 1

Sorry if you actually tried the obvious one but have you set Firefox as your default browser in Preferred Application settings?

For me Firefox is set to default in Preferred Applications AND in Firefox.

Answer 2

it turned out it was a bug in thunderbird.

bugreport

After upgrading thunderbird to version 1:91.7.0-2~deb10u1 this behaviour is gone.