Describe the solution you'd like
I would like to rely on support for 'urn:xmpp:mam:2#extended' specified in xep-0313.
https://xmpp.org/extensions/xep-0313.html#query-paging-flip
I have the same question!
Can anyone offer an alternative?
My project depends a lot on this functionality.
I've implemented support for Flipped Pages as described in https://xmpp.org/extensions/xep-0313.html#query-paging-flip
Notice that #extended is not advertized, because that would require implementing other features, like https://xmpp.org/extensions/xep-0313.html#archive-metadata and https://xmpp.org/extensions/xep-0313.html#query-limit-id
Most helpful comment
I've implemented support for Flipped Pages as described in https://xmpp.org/extensions/xep-0313.html#query-paging-flip
Notice that #extended is not advertized, because that would require implementing other features, like https://xmpp.org/extensions/xep-0313.html#archive-metadata and https://xmpp.org/extensions/xep-0313.html#query-limit-id