Hello, I am going to investigate this issue. Here are a few questions:
- Which Render Pipeline are you using?
- Which package are you using for building your UI? I’m guessing this is Unity UI @ 1.0.0
- Can you please share a screenshot of your Recorder settings? I assume you’re recording the GameView.
Also, we released 4.0.0-pre.1 recently, you should upgrade 
I just tried in 2021.1.15f1 with Recorder@4.0.0-pre.1 and I can see my text in the export, both images and movies (WYSIWYG, if it shows up in the GameView you should see it in the export).
Can you try a very simple canvas setup like mine?
