Is there a standard way to add some approval procedure/or at least notification for changes in task groups/builds/etc.?

We had a few cases when:

1. Someone changes a task group (or build/release/whatever).
2. Makes some mistake.
3. Then publishes/saves it.
4. But doesn't notify anyone that such changes were made.
5. Some hours later some dependent build breaks because of those changes.
6. And we have to spend even more time trying to find what and when has changed as it is not often that simple to find out with external task groups.

What we want to have:

1. Ideally - some approval process for such changes. Kind of like code review, but for task groups/builds.
2. If not - then at least some way to receive notifications about changes in task groups and etc. we are interested in?

I found neither, and, honestly, doubt that such features are present in the TFS version we use (TFS 2018.2), but perhaps I've missed something.

There isn't any workflow security or approval process for the groups. You could suggest that kind of feature on the developercommunity. Restrict access to edit Task Groups to only those who understand how to bump the Task Group version. That way at least you will keep backward compatibility across your builds unless that explicitly upgrade to that version.

There aren't any built in notifications, but you could create an automated process to send email notifications using PowerShell using the existing API.

1. Get the Id for the task group using the taskgroups list api
2. Use the revisions api to get the history _apis/distributedtask/taskgroups/{taskgroupid}/revisions
3. Send an update for anything that edited today