With Mac OS X Catalina no longer running 32-bit apps[1], it was time to me to begrudging upgrade from You Need A Budget 4 to You Need A Budget 5.
This necessitated a total rewrite of the importer I wrote over 2 years ago[2]. The good news is that YNAB's new cloud-based app has a fully functional API.
Here's the new importer for YNAB5:
It seems to work in my personal use and with limited testing of things like split transactions, scheduled transactions, tracking accounts, and so on. If you try it and something doesn't work, send me an email.