Synapse v1.14.0 included support for room version 6 (see #7500). At some point we'll want to make this the default once people have had time to upgrade to compatible homeservers.
Just a suggestion, I personally think that it would be a better idea to fix the issues before making it the default:
https://github.com/vector-im/element-android/issues/1558
https://github.com/vector-im/element-android/issues/1879
Fixed by #8461
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MSC: https://github.com/matrix-org/matrix-doc/pull/2788