The one I read required a double blind controlled study that injects the isolated alive virus into multiple humans/at least primates which then have to develop symptoms. I guess if somebody did that they would move the goal posts again.
On your page I can't even find a definition of what they would accept as "scientifically prove the process of isolation".
[1] https://www.embopress.org/doi/full/10.15252/embj.2020106230
* "Severe Acute Respiratory Syndrome Coronavirus 2 from Patient with Coronavirus Disease, United States": https://doi.org/10.3201/eid2606.200516
* "Isolation and characterization of severe acute respiratory syndrome coronavirus 2 in Turkey": https://doi.org/10.1371/journal.pone.0238614
The website also has an article titled, "Die Virusexistenzbehauptungen von SARS-CoV-2 sind eindeutig widerlegt," which translates to, "The claims of the existence of the virus SARS-CoV-2 are definitively disproved."
Typical pseudo-scientific conspiracy theory FUD.
Virology is not my field, but I understand enough to follow the papers I linked to above. They describe the isolation of live/active virus from patient samples. There is active research with cultured SARS-CoV-2 virus in BSL-3 labs around the world. It's just bizarre that there are people who believe the virus doesn't exist, or that it doesn't cause CoVID-19.