Hello,
Good day!
If the job titles of users contain the common word "Dev," you can utilize the following dynamic membership rule to create the dynamic group: (user.jobTitle -eq "Dev") or (user.jobTitle -match "Dev").
Regarding SharePoint, each channel site operates independently in terms of membership management. Therefore, changes made to the membership of the main SharePoint site do not automatically propagate to the channel sites. If you wish for the membership of the channel sites to also be dynamic based on Azure AD group membership, you would need to configure each channel site separately to utilize dynamic membership rules based on the same Azure AD group.
Regards,
Lakshmanan