The #xmpp OMEMO ecosystem is still a bit of a catastrophe: There are four namespaces for omemo, omemo:0, 1 and 2 and the axolotl one and we have version 0.8.0.
Every client implements 0.3.0 of the OMEMO extension, which isn't cryptographically insecure but has worse key exchange (and no cross signing) than 0.8.0 + related.

There is ONE client which implements omemo 0.8.0 but has a toggle to use the older version.

Edit: axolotl = signal protocol with the same key exchange, I forgot