Hello again. I have just tested it on Unity 2020.3.0f1 and it works as expected. The upddated webgl demo is built on that Unity version as well, you should be able to see it working on this same page.
Can you elabotate a bit on the issue/s you was experiencing? I see no breaking changes on Unity's UnityWebRequest that affect Google Sheets For Unity.
Thanks again for the generous patience :)