We built some tools in house. I would say we have a fairly pedestrian system. We do B2B software, so there is some build time configuration and enforcement we like to apply from a project management perspective.

90% of our struggle is addressed by the fact that our product is a single binary distribution that only needs to be installed on 1 host. The self-contained deployments option provided by .NET is very helpful too.

The way our process works - someone merges a PR down and a project manager is looking for a build containing this for testing. So, they will log into a system that is integrated with github to trigger a build at the desired commit. Once it completes, the release artifacts are zipped up and sent to a public S3 bucket using a csprng token as the file name. This link is surfaced in our interface for easy handoff to the customer in email. For internal purposes, the project manager can optionally perform automatic deployment of the completed build to one or more internal environments. Automatic, scheduled delivery of the release email to customers is also an option.

We also employ some 3rd party tools, such as github actions to run checkbuilds and gate merging of PRs.

Ultimately, the theme of our toolset is to empower non developers to move mountains. You can get some of this with 3rd party, but you'll never have it fit as well as our solution does for us.