We have a collection of peer reviewed research on some mechanisms for entry due to other viruses allowing us to infer from other 'similar' viruses and confirm the portal of entry by studying tissues of affected individuals.

What's called the chain of infection within virology tends to follow similar modes of entry for similar viruses. Generally the main differences between species and sometimes individuum are that they targeting different receptors of the same cells. The studies showed that under study the physiological reaction to infection indicated that the portals of entry that have been hypothesized are significant in their likelyhood as portal of entry.

Do you have peer reviewed research for me to read that states differently? I most likely have access to it if you do have one.

This subject has been researched heavily since the onset of the pandemic and there's a lot of peer reviewed research. Some fraudulent articles as well, so make sure they're properly reviewed.