This is a large task list, and many of these things will require a lot of time and effort to implement properly. Especially given the language spread, where a different solution is often required for each language, you'll need to prioritize effectively to make effective positive change (not easy, but important).
Those changes should ideally make developers' jobs easier, but it should also improve the security and quality of the systems. The priorities depend on not just what developers see as friction, but also what's important to the business.
You don't always get to make everyone happy, but one example at my company is that we implemented [OpenID Connect](https://docs.github.com/en/actions/deployment/security-harde...) with our GitHub Actions and Artifactory installation to enable passwordless auth for uploading build artifacts as part of a CI build. This let developers not have to deal with managing a password for Artifactory, and also made security happy because that's a lot less passwords floating around.
Another idea that's helped the comradery and quality of our teams is language-specific working groups. My company has a few thousand developers, so establishing a monthly meeting where you share ideas, and facilitating discussions of recommended paths is useful. Your job as developer advocate can be a facilitator of the objectives and tasks, and run the meeting. Again, it's a significant time commitment, but has been very valuable for us. To emphasize; you're paving paths, not building walls. This is key to avoid preventing teams from deviating as needed, but also attract those that are looking for a smoother way of getting where they're going.