But to get it into the mainstream, it needs to compete with other messaging apps such as Telegram.

For that, it needs polish. Period. There's no way around it. So if the goal is to get it into the mainstream (and personally, I want it to be), then that is what it needs.

There are loads of ways you can contribute to this:

1. Contribute time, code, designs, general help and volunteering

2. Contribute money via personal means or via work

3. Promote the use of Matrix to individuals

4. Promote the use of Matrix to businesses, eg. at work, or as a backing protocol for messaging where it makes sense etc.

5. Purchase products that make use of or contribute to Matrix

etc. But in order for it to become popular on its own, and acquire a network effect (which it needs, because IM apps are a class of their own), friction to get new users needs to be reduced to near-zero. And for that... polish is needed. That's it.