Yes, I am having this same issue. Lightroom 3.2.1 in Catalina. Export bar just sits at like 3%, never progresses. Also using Dropbox for file sync; I had read somewhere that it may be conflict, but that "fix" didn't help either.
To make matters even more confusing, mine seems to be working now and I didn't do anything - I didn't even restart my computer. It just decided to work. But now whenever I go to export a photo I can't help but thinking "I hope this works"
If anyone has a fix they know of it would be appreciated. Or if Adobe actually did something, that would also be great.