This is most likely a Chrome bug, that has been around for months. I decided to report it here, since I figured you might want to track it and perhaps you have some Google dev contacts. After all it impacts all your end users and users of other similar platforms.
Based on my own tests, user reports and discussions around the web this is most likely to happen on Android 10 running a latest production Chrome. The issues have been around atleast through the summer.
To reproduce one simply writes or edits a message and Chrome freezes - typed text stops appearing. The situation may resolve by waiting a while, or as a workaround you can tap Home button and then back to Chrome --> it unfreezes.
I have not tested Beta or Dev branches of Chrome to see whether this has been resolved. Also I have not found any comments by Google devs on the matter.
So, if your Android device freezes on a Discourse site, the reason is most likely not in the community platform. Here is a Reddit thread for more background discussion: