@90bear Everything you've said is wrong. When a server is overloaded, it puts requests in a queue to be served. Most of the time, the queue doesn't discriminate by client OS. It's first-come, first-served. If a response hasn't been received by the client after a certain amount of time, the request is timed out. It's that simple. It has nothing to do with wifi or OS. The servers are simply overloaded.
While your reasoning for it is also completely wrong, using a VPN or a different DNS server can allow you to connect to a server in another region that might not be overloaded.
The issue is site-wide and occurring for all users. All of the troubleshooting steps you've mentioned would only be useful if the slowdown was only being experienced by a single user or a small subset of users.
TL;DR: There's nothing anyone other than the site administrators can do to fix this. The only fix is to upgrade the current servers or spin up more servers to meet user demand. That's expensive and time-consuming, though. So, we'll just need to wait until the admins address the issue or until the COVID thing dies down and server load is back to normal.
Edit: Removing bloatware won't void your Windows license. Mircosoft offers a clean install tool to remove OEM bloatware. https://www.microsoft.com/en-us/software-download/windows10startfresh
WiFi 6 is 802.11ax.
BSD is based on UNIX. That alone proves it's not the origin of OS.
BSD came out in 1977. The first use of TCP/IP was in 1975. Also not the origin of the internet.
A PDU from a Windows client will be identical to a PDU from a Linux client. There is nothing in the header of a packet, segment, or frame that identifies what OS the client is using. It's possible to determine a client's OS through other means, like using javascript or looking at the client's response from a malformed data unit, but that has nothing to do with the network stack. While you talk about the Linux network stack being better than Windows, you don't point to anything in particular. Each stack has its advantages and disadvantages depending on the situation. If you want to discuss a specific deficiency of one over the other, that's fine, but it's incorrect to make a blanket statement like that.
Edit 2:
It's usually best to leave channel selection to the wireless AP rather than to select a static channel. Channel congestion can change over time. Most APs can analyze channel congestion and change the channel on the fly if there are any issues with RSSI or latency.
Your explanation about 'resolving approach' is nonsensical. I assume you're talking about congestion control. That's handled completely by the server and has nothing do to with the clients. Congestion control reduces the bandwidth allocated to each client or reduces transmission rate until the congestion has been resolved. If the transmission rate slows enough, the request will time out before it's served. It has nothing to do with the client OS.