So how do you set them?
On Desktop there is a Optional permissions for added functionality: under permissions, but it’s missing on Android.
Any ideas or is it a bug?
It is not fully implemented on Android, see also the details in the compat table on MDN:
Thx, but that seems a different (related) bug.
I don’t use permission.request(), because Starting with Firefox 84, users will be able to manage optional permissions from the Firefox Add-ons Manager.
And that compat table shows full support for Android
Bug report