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Will a Covid test recognize a regular flu virus?

I don't know. Diogenisis up thread suggests that could be the case. It would not surprise me in the least.

What is apparent to me is that Covid is spiking while flu has practically disappeared. I try to live in a world called "reality" and until someone can give me a good explanation as to why this is the case, I will attribute it to them adding flu in with covid numbers. That is what make sense to me.

Will a Covid test recognize a regular flu virus?

Yes and no. The PCR test simply takes DNA in your sample, and doubles it. After several cycles, you have large amounts of whatever was in your sample, making it easier to look for a particular sequence of DNA. So yes, it boosts influenza DNA in the sample, but if you're only looking for coronavirus-specific DNA, it won't count. Part of the problem though was that the short sequences of DNA they looked for / found, might sometimes be a part of DNA that the ChinaVirus has in common with any of the four other coronavirus strains that cause a common cold. So, a common cold could have popped you hot for the ChinaVirus.

The PCR test is used for IDing several hundred different possible infections, and is generally used to figure out which one you have when you show up to the doc sick, so they know how to treat it. Usually they'll individually test for flu/strep/other stuff first, as a PCR is much more expensive than / not as immediate as the simple basic tests, and most of the time those will be what you have. It is sheer medical stupidity to try to use a PCR test to "diagnose" if a perfectly fine person is infected, as you'll generally still have (dead/inactive) particles of a prior infection in your system for months after your system beat it off. OR, you might have a few particles of the virus/bacteria in your nasal passages, but your body successfully fights it off (nasal mucus is one of your very front-line defenses). You'll possibly test positive from a nasal swab, even though you never were actually infected.

The antigen tests, which are the rapid 15-20min tests, look at proteins that reveal the presence of the virus. these are much more specific to a particular type of protein, but I have no clue how many or which proteins are shared across different viral groups, or how wide of a net they are. ChinaVirus and influenza may share some, or none, of their proteins, but as above, the ChinaVirus certainly shares some proteins (maybe all) with other coronaviri.
Antigen tests are generally considered very reliable on positive results; however, a negative test is usually I think about 80% accurate so that means 20% of negative cases not only go undetected, but believe themselves to be uninfected.

Antibody tests (usually a blood sample) look at antibody presence, but they're not a good indicator of current infection/infectivity at all. You don't usually get a good amount of antibodies in your system until a decent time after you've been infected, and antibodies last in your system for a while (at least nine months per a poster on another thread). So useful to see if you have some immunity, but useless to determine if you're sick or not.