This is what I did to unlock the read and unread options and maybe worth trying if you still don't have it.
Connect to wifi and do a sync.Restart kindle oasis 2.
This gave me the filter and sort option but still no Read and unread selection.
I had to again connect to wifi and do a sync and while still connected to wifi put the kindle to sleep/close cover. Wait 10 seconds and turn it back on. I have now unlocked the read and unread options.
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