Animate 2020 can't publish to HTML5 canvas without image export

Due to secific requirements for my projects, I need to publish to HTML5 canvas, but can't use image assets, so in publish settings I untick "export image assets". I've been doing this for several years and it has never caused an issue, as there are no images imported into my projects, it's all vector graphics done in Animate.

Since updating to Animate 2020, this doesn't work. Even if I start a brand new HTML5 canvas project, just draw a square on the stage, then go to publish settings and untick "export image assets" and then publish, then if I open it in the browser it will just be a blank screen. If I open the developer console in the browser it says "TypeError: f is undefined". I've spoken to Adobe support on the phone, but their reply was just "You have always needed to export image assets, there's nothing I can do to help you".... great.

I've been using this software since it was Flash 4, and the decision to continue with Adobe Animate was based on the assumption that it would be relatively future proof. The short term solution has been to revert back to Animate 2019, but this clearly won't suffice forever.

For the love of god Adobe please fix this. The cost to my business to have to find new software that does the job, and then train everyone to use it, will be immense. I have been screwed by Adobe many times over the years but I think this may be the final nail in the coffin.