SVG Favicon background

This is not a typical bug-report-type of question, which is why I am not using the template.
I am currently using an SVG-file with quite a lot of transparency as my favicon. I am running Nextcloud 23 with Breeze Dark theme (if thats relevant…) on Ubuntu 20.04. My favicon works, but there is a square grey background color. I think that this is most likely a configuration error by myself. How can I get rid of it?

Best regards