What exactly do you mean by "group text" – group SMS? SMS was never meant for group communications. If somebody replies to your SMS, only you (and no the other recipients of your original message) will receive the reply.
The stock (AOSP) messaging apps works just fine. Can you send SMS to single recipients?
I have installed sandboxed Play Services and Google Messages for RCS, which works fine with Deutsche Telekom in Germany.
For instant and group messaging I use Signal.