If you have a look at enough research then you'll find enough detail and proof that it's beyond reasonable doubt (I really think you should be using "balance of probability", not "beyond reasonable doubt")

The spartacus letter has a lot of detail and is well sourced at the end. That's a very good start, and so is generally looking at ACE2 receptor interaction with the spike protein and watching videos by people like Professor Dolores Cahill and Dr Lee Merritt.

https://www.theautomaticearth.com/2021/09/spartacus/

When you study it for a while, you'll stop believing it doesn't exist just to make your thinking less complicated.