Yes, unfortunately today Connect does not have a way to read the groups from the linux operating system and instantiate them inside of Connect.
However, it is possible to automate this type of task with the RStudio Connect Server API: https://docs.rstudio.com/connect/api/
(User cookbook here: https://docs.rstudio.com/connect/cookbook/)
In particular, there is an R package that can simplify some of these tasks if you wanted to write the work yourself. You can create groups, assign memberships, remove memberships, etc. The important task would just be ensuring that you have a way to read group memberships in a nice way.
Is that a task that you would feel comfortable doing?
In the meantime, I will definitely share this feedback with our team! We always enjoy hearing which features would be useful. Are you managing groups on the linux server yourself, or are groups coming out of an LDAP server / Active Directory somewhere?