I expected this to be quickly confirmed but it hasn’t been. Is anyone else seeing it? Maybe it’s just my devices - all are all quite old - AOSP 4.4 and 5.1.
I installed an addon yesterday and it shows no options either so it’s not just my own.
(I have webextension versions of both my SDK addons but options_ui is not implemented on fennec yet: bug 1302504).
Added: I discovered that it’s not just SDK/simple prefs. All prefs do not display in Fx 51 for Android for me.
(Unfortunately, in trying to test this I discovered that both my Android tablets are not supported by Fx 53 because they have non-NEON processors - bug 1344906. )