Allow group based channel sharing - e.g. everyone

For your scenario, I recommend using Viva Engage, which is designed specifically for building communities across the entire organization. Unlike Teams, Viva Engage allows anyone in the organization to join and participate in community spaces without the need for invitations or manual membership management. It provides a seamless way to foster communication and collaboration across teams, with the ability to highlight key members or roles. It’s the ideal solution for creating a tenant-wide "get in touch" channel, reducing administrative overhead and encouraging broader engagement.