Do we have a list of servers that are safe for sure? Would help because then you could connect manually to those when you get the pop up.
Such a list is not very useful. Keep your Electrum updated by checking electrum.org, this is our only advice.
The only thing a malicious server could ever do, is to display error messages. Because Electrum v3.3.3 doesn't allow the server to display arbitrary error messages, it is safer.
If your Electrum v3.3.3+ version is showing error messages when trying to broadcast a transaction, as of right now, it probably means that you are currently using a malicious server. In that case, you can choose another server using the network dialog.
I work for Electrum Technologies GmbH.