This page might help, it explains what alternative UIs are and which ones are available. Some of them can also be used in the mobile web browser.
https://fedecan.ca/en/guide/threadiverse/alternative-uis
(It says tesseract is available on lemmy.ca, but that is out of date now)
This issue with Tesseract affects anyone that was using it. So it is possible that someone did not see a comment or post you made, without knowing why they could not see it. Past that, it likely hasn't affected you since you said you don't use it :)