Group rides are a lot of TSS. Accomodate them or skip them?

I don’t think you necessarily need to do that if you find that you can handle the load. For the reasons mentioned, and as indoor:outdoor TSS are not quite 1:1 in terms of effort.

After Sunday you have Monday as rest. If you don’t experience a negative carry-over effect on other workouts in your plan, I would say enjoy the group ride and don’t adjust. But be aware of possible effects.