Quest 2: Can't use https download in signed build

I have an android application that executes an http/https download. That application is for windows and for quest 2. I am pushing the builds to the quest via sideloading, so no store involved yet.

My builds:

development - works like a charme

Shipping - works like a charme

Shipping with “for distribution” marked and signed with an keystore - doesn’t work

There are no other difference to the project or the project settings.

What could cause this?

Permissions? I have in the manifest:

WRITE_EXTERNAL_STORAGE

INTERNET

READ_EXTERNAL_STORAGE

I also have android:usesCleartextTraffic=“true” in the manifest although both http and httpa don’t work.

Tried full rebuilds, also don’t see any errors in the packaging or in the device log of the quest 2. All I can say is that it looks like the download never starts. The tool has an error messaging if it is aborted or successful, but that never fires. Trying to print the currently downloaded bytes always says 0.

Banging my head against this for 2 days now. Any idea is appreciated! Thanks!