Just realised I didn't have a pnut.io app on my new (spare) Android phone. So I downloaded Goober from github and shared it via my Dropshare app, available via Setapp subscription. Dropshare is linked to a folder in OneDrive, so I downloaded OneDrive from the Google Play Store and accesses the .apk file on the phone.
First I had to tell the phone it was OK to install stuff from an unrecognised developer and later to install the app anyway, despite it supposedly being unsuited to the OS version I have.
it works fine.
then I thought, "why didn't I just use the phone to save the download. I followed up the Dale app from the pnut.io website and it side-loaded quite successfully, too. Just to be on the safe side, I also saved the beta.pnut.io web app to the desktop as well.