Hi lansti,
I think I can help you out. Did you have a look at my blog post? The same magic applies to configuring the default browser.
https://www.ivandemes.com/export-import-file-type-associations-fta-successfully-using-uem/
Like UEMdev mentioned, if you got any more questions or reactions regarding your topic, can you please open a new thread? Just so we don't get things mixed up. I am glad to help you out with the required steps if necessary, so please let me know.