There shouldn't have to be a work-around for freezing groups in Ableton. Ideally this is something that should just be possible under the hood, especially with a work-around this simple, you'd think it would be easy enough to implement in future updates.
"In ableton we don't have the option to freeze grouped tracks, which is annoying. There is a workaround though.
1) Create new midi track
2) Add Compressor
3) Open sidechain settings
4) Select Bus that you want to freeze
5) Click on the headphones that allow you to hear the sidechained signal
6) Create an empty midi clip that aligns with the section of the group audio that you want to freeze
7) Make sure the EQ on the compressor is off as not to interfere with the signal
Freeze the track"