Removing signature dashes in Evolution

Hi! I have installed Fedora Silverblue 43, connected my email account via online accounts and installed Evolution from Fedora Flatpak repo. I added a signature to Evolution and wanted to compose an email. An editor window shows up with my signature and above it two dashes. I’m aware the double dash is defended as necessary, due to being mentioned in some RFC. However, I really want it gone.

Looking to remove these dashes, I found this fix:

dconf write /org/gnome/evolution/mail/composer-no-signature-delim true

However, that doesn’t give the desired result, the dashes are still added. Dconf-editor shows me the key, however tells me there is no schema for it. There aren’t any other keys in /org/gnome/evolution/mail. Looking in the Git repo, the key is mentioned in the schema file.

What am i missing, how can I fix the double dash issue?

I think you need to set that inside the Flatpak sandbox. I vaguely remember someone giving an example in a thread here but I can not find it anymore.