This is tautological, sub-saharan genetic markers are found predominantly in sub-saharan populations by definition.
Given how humanity has evolved, "european" markers are a subset of the diversity found in subsaharan populations that are overrepresented from founder effects, with very few exceptions. 40,000 years ago sounds like a long time, but it really isn't.
You need an amazingly small amount of migration (about one person per generation) to keep a population in sync with each other genetically.
I have no idea where you get your graphs from - the chart you want is this one:
https://www.cdc.gov/flu/weekly/weeklyarchives2019-2020/image... (pneumonia and influenza mortality, COVID kills via penumonia and as such is in that graph), the spike at 2019-50 is the normal flu reason (you can see we were having a slightly above normal one that started to decline out), the spike at week 10 onwards is COVID-19. Likewise, looking at ILI (influenza like illnesses), you can see the normal flu season spike near week 50, a decline towards baseline, and then a rise towards week 10 https://gis.cdc.gov/grasp/fluview/fluportaldashboard.html (ILInet line graph), followed by a decline as stay at home orders began to come into effect.
COVID emphatically was not circulating in numbers in november. We would have noticed, same as the chinese did, from the massive increase in pnuemonia clusters. Genetic analysis backs this up. You don't know what you're talking about, again.
You have no cause to sound as confident as you are. You're completely wrong in the first paragraph in a way that shows you don't understand the first thing that you are talking about. For example, you say " For instance, covid19 was discovered around October at the start of the seasonal flu season in the northern hemisphere and it was a coronavirus, which makes it 95% likely to be strongly seasonal, highly infectious, and mild"
First, it was discovered in late December, probably jumping to humans in November. Second, there are four "mild" coronaviruses, that have been circulating for a long time, but that's neglecting to mention that there is a strong bright line between the "seasonal" circulating coronaviruses and the new coronaviruses - the name that was given to nCoV-19 gives a hint to what you should be calibrating as your reference (SARS-CoV-2) - SARS and MERS, both of which have astronomical case fatality rates (10% and 40%). SARS was contained by a massive public health effort of quarantine and lockdown, MERS the same except it seems to be less transmittable.
Given how humanity has evolved, "european" markers are a subset of the diversity found in subsaharan populations that are overrepresented from founder effects, with very few exceptions. 40,000 years ago sounds like a long time, but it really isn't.
You need an amazingly small amount of migration (about one person per generation) to keep a population in sync with each other genetically.