The r-lib/r-azure-pipelines example repo still works, even if R-lib seems to have moved on to Github Actions. You can also look at my AzureR packages for examples of simpler Azure Pipeline workflows. Here's one:
You can ignore the 'copy to cloudyr' and 'update cloudyr drat' steps in the azure-pipelines.yaml file, they are specific to my pipeline. Everything else is fairly generic.