(FYI, Element is also a Matrix client, though it’s business/enterprise focused)

There are 2 things to consider.

First, demand. Us being vocal about it is one thing, but the real demand may be low. We moved our community from Discord to Matrix - While a direct migration wasn’t possible, we setup a Discord bridge for 6 months during a transition period which was invaluable. The bridge kept all our chat history which we can still see today even though the bridge is down and the discord server got nuked.

Second, priorities. Unless a PR is submitted by a voluntary, the 3 platforms you mention have limited resources and higher-priority items that need to be worked on.