14.2 h.264 bug
I think I've figured out the problem with the latest 14.2 export issue. Nothing on my system has changed except for the 14.2 update. When I select export within Premiere, the dialog box would not open or it would open but freeze Premiere if I select h.264 or h.265. After reading more about the latest update, it appears that this new version uses hardware acceleration on NVIDIA or AMD processors when encoding. Prior to this, Premiere used Intel QuickSync when encoding, which it what it was doing on my system. The new update switched to my NVIDIA to do the encoding which is where the problem seems to lie. Premiere and my NVIDIA GT 1030 do not work well together at this point. I confirmed this by switching off hardware encoding to software only in Premiere's preferences. When I switch to software only, exporting works as normal.
Antoine Autokroma commented
Try exporting with AfterCodecs Exporter for Adobe https://www.autokroma.com/AfterCodecs/