Yes, Tab group is deprecated and removed from layout palette as well. We have 'Layout Group' added to replace 'tab group', however looks like your requirement cannot be achieved using layout group. We would consider this usecase and try to implement in future releases.
For now if you need Tab Group for your requirement, you can open 'pzStudioContainerTabs' OOTB section where there is tab group layout included.
You can save as this section into your application ruleset and make use of it.
I was able to see the section with the help of live UI.But this section is already having warning as per best practice(Section uses the following formats that are not defined in the pyEndUser71 skin: Temporary top tabs).