Version of Rocket.Chat Server: 6.9.3
Can you check your snap version please? I think you should be on 6.11.1 or at least 6.10.4 as your version has a security hole you need to fix.
Could you please let us know if there is a possibility to globally disable text formatting (if I’m not mistaken, Markdown is responsible for this)
Used to be this (if you search here) but can’t see that as a setting right now.