https://compliance.conversations.im/ not for clients but slowly getting there for the servers. And this is only for a working text-based chat, AV is really of the table. Basically except for conversations, most of the "clients" should be labeled protocol explorers because most of them have serious usability issues with most of the listed XEP...
The worst thing isn't that the standard isn't defined or something, but that a lot of projects are claiming to support XMPP when they only support some core functionality...
then we could see an estimated total, like for $xx we could get most of these apps all on the same page of features running... if that is the major hurdle - a crowdsourced money or and time to get them all modernized may make the whole ecosystem 2.0 and worthy of use?
Surely it can't be that much that is needed - yet it seems that fixing just one or two is not having the same network effects of having them all speaking the 2.0 feature language.