Option 1: Everyone develops on the CI/CD platform.
Ops gives devs "disposable environments" to do their testing in. Basically, GitHub + Jenkins + Terraform + AWS. I've used this to stand up real infrastructure every time a PR is opened, and pipelines run against the infra. Code and infra match each other because they both exist in the same branch/repo (monorepo; you can of course do multi-repo, just takes more coordination). It's all destroyed as soon as the PR is closed, but you can also keep it up to do dev work against. You can also keep one copy of the latest master branch up at all times (the "dev" or "cert" or "test" infrastructure) as a shared test environment. Downside: you have to have access to the network (which is in AWS, so that's not so difficult). Upside: the dev environment always mimics production, devs don't need to do anything to stand it up.
Option 2: A bunch of mocks, and scripts to stand up stuff in Docker, using docker-compose or something else. This becomes a bit of a problem to manage with lots of devs, though, and docker-compose is not a good model for production deployments.
Ops gives devs "disposable environments" to do their testing in. Basically, GitHub + Jenkins + Terraform + AWS. I've used this to stand up real infrastructure every time a PR is opened, and pipelines run against the infra. Code and infra match each other because they both exist in the same branch/repo (monorepo; you can of course do multi-repo, just takes more coordination). It's all destroyed as soon as the PR is closed, but you can also keep it up to do dev work against. You can also keep one copy of the latest master branch up at all times (the "dev" or "cert" or "test" infrastructure) as a shared test environment. Downside: you have to have access to the network (which is in AWS, so that's not so difficult). Upside: the dev environment always mimics production, devs don't need to do anything to stand it up.
Option 2: A bunch of mocks, and scripts to stand up stuff in Docker, using docker-compose or something else. This becomes a bit of a problem to manage with lots of devs, though, and docker-compose is not a good model for production deployments.