Both RATs and PCR tests are absolutely specific for the Covid-19...

Both RATs and PCR tests are absolutely specific for the Covid-19 virus (SARS-CoV-2), including all variants, and definitely cannot be triggered by another viruses, including influenza or common cold viruses.

The whole "false positive" claims that are floating around the internet regarding Covid-19 are completely wrong, and as far as I can see, actively designed to be misinformation about the pandemic.

The omicron variant of the virus has quite a lot of mutations compared to the original Wuhan strain, but it is still detectable, as most of the mutations affect the spike protein. The PCR test amplifies three different genes of SARS-CoV-2, and in the case of omicron, the part of the spike gene targeted by the PCR is mutated and doesn't amplify. This is the so-called S-gene dropout, and helps identify the omicron variant, where the S gene doesn't amplify but the other two genes do. And as I mentioned earlier, the RATs identify parts of the the nucleocapsid and envelope proteins, so again, aren't affected by any mutations in the variants.