Find recently changed repositories with a specific name

I’m using GitHub Enterprise, but I think, the search syntax of GitHub applies there as well.
In my project I have to maintain over 50 repos. So I need to find out, which of them were changed in a specific timeframe.
According to the GitHub Help you can use the search function with the pushed qualifier

So I’ve tried this in GitHub Enterprise with e.g.

<reponame> pushed:>2019-10-01

but I don’t get any results, although there were some commits in October.

Maybe this is an issue because my repos are private?

One additional wrinkle is that search only works on the default branch. So if the repository you’re looking for has only had activity on non-default branches, then it wouldn’t show up in the search results. But if you search for only the repository itself, then you could iterate across the branches in each of them and see what the latest commit was on each.

Let us know if you have more questions.