Like the recent news from Fairphone and their Fairphone Open, a LineageOS fork, microG, also brings freedom with options. On their build, the free-open-libre repository F-Droid comes in a “bloatware” fashion (sorry )
I cannot say if it’s necessary to allow the Unknown Sources, but after clicking the download option of any app on the F-Droid GUI, the app will be downloaded and installed straight away, without any further screen tap.
PS.: already mentioned on the comments of their blog post