How about a choice of Google Play Store or direct download, for "Advanced" users? That's all I'm asking, just a tiny little 8pt font link to directly download the APK.
Why would a business host a APK directly when they can just utilize Google's infrastructure for free? Likely you would have a lot of users mistakingly download the APK if they saw the link and get confused as to why it's not working like all their other apps, whereas downloading from Google Play Store works seamlessly.
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.