Based on comments by a few new users to the forum, this occurred to me. Maybe I’ve missed an explanation somewhere, but I couldn’t find it.
Why isn’t a copy of the APK available in GitHub under the Assets section of each release?
A couple of my other favourite apps have the APK in the Play Store, F-droid, and GitHub. Especially for those who want the latest but don’t use the Play Store and because F-droid is often slow to update.
Because uploading them is more work for me 
If someone agrees to care for pushing beta releases to F-Droid (experience with git needed), we can do that (see my comment on GitHub).
Staff edit: the comment on GitHub was marked as off-topic together with some other replies. Click on ‘Show comment’ to see ByteHamster’s explanation.
You can’t really circumvent that because F-Droid gives the apk its own signing key so if you use a github apk, you won’t be able to update automatically but rather, have to check the github releases page for a new version by hand each time you THINK there might be an update.
You’re better off asking the F-Droid team to speed up their update rollouts.
You can also use the Apkmirror version which is the same key as Google Play. You can then use an Apkmirror updater app (such as APKUpdater) to update Antennapod.