Could Authy be of use for you perhaps? It seems like they have a desktop app, although I have no personal experience with it. Alternatively, GitHub supports the use of Security Keys which are physical devices that you can purchase for 2FA purposes, Yubico works great in my experience but there are other manufacturers, or even DIY solutions.

They have one now at social.overheid.nl which they seem to test at the moment. They have a few accounts such as Belastingdienst, KNMI, Rijkswaterstaat, MinBZK so I hope they’ll continue after the experiment phase is over.

Would it be possible to have the subscribe option appear as a long press of the icon as well? I’m finding the plus button to be an uncomfortably small tap target. I totally glimpsed over "Join", my bad.

Thanks for building a great app!