Then host the APK on GitHub. They don't have to host source there as well. And I'm sure they can design a page in such a way that only the more technical potential customers go for the direct download.
It's also rather ridiculous that these services are accessible/usable/activated only via an installed app on my phone or tablet. Just make the service available via my web browser and the issue is resolved.
In the end I just don't bother with these services - N26, Monzo and now Revolut. I'll just stick with TransferWise.