Ask HN: What's your feature testing workflow?

At my company our testing workflow for web projects looks like this:

1. A developer creates a PR on Github(which triggers a build on CI and runs automated tests)

2. A developer deploys a branch with a feature to one of the staging environments

3. A QA engineer and a Product Owner go to the said staging server and do their review

4. Once PR has been reviewed and passed QA/PO review it's merged to master and ready to release

My pain point with this is actually a management of staging servers. We always have to ask each other "Hey, is staging server X free now? Can I take staging server Y?". There's a fixed number of them, and we don't have a system in place to keep track of what's currently in use. How does it look like for you?