Who deploys/manages upgrades?

I work at a relatively small company with an engineering team that is mostly focused on building new features of our application. We ship new features/releases every 6-8 weeks.

Although the app is the same for all clients, this application is a single-tenant B2B app. In other words, each client gets their own environment that requires frequent updates every couple months.

My question is with regards to shipping upgrades. Who does this work in your organization or how does it work and who does it?

Just looking to get some inspiration on how orgs out there perform activities such as:

• Coordinating or announcing a maintenance window to upgrade
• Coaching customers to upgrade
• Explaining new features
• Tracking customers and what version they are on