It seems that community contributions to Element Web (Matrix client) are often effectively rejected. For example, see:

• https://github.com/matrix-org/matrix-react-sdk/pull/9240
• https://github.com/matrix-org/matrix-react-sdk/pull/11078

There are also many other PRs for Element Web/Desktop which have not gotten a review in a timely manner (see here). The request to improve the terrible notification sound has been there since 2017, and though several PRs have been submitted to improve it, they have been either ignored or rejected for an unknown reason (there should be an epic project going on which should make the six-year-wait legitimate).

When it comes to development of Element, there is a lot of unspoken, unwritten, internally shared rules among the internal team members. Your PR will be effectively rejected even if it works, unless it aligns with their goals, which you cannot know before submitting a PR.

It should be well noted that there is a clear and strict division between the internal paid workers and external volunteer developers who essentially provide the team free labor. The exclusive attitude of the team behind Element has discouraged the latter from contributing to the project. I myself have been one of the active localization volunteers, but I stopped contributing after I realized it has been free labor.