EOL means no more security updates, which means attack vectors don't get patched.
If you keep using a Windows installation (or any OS for that matter) that isn't patched regularly you are very likely to be victim to some malicious actor eventually. It's not manual hacking anymore, it's bots scraping the whole internet exploiting known vulnerabilities completely automated.
The risk is much lower if you're in a home network with NAT, where your PCs IP is not publicly reachable, but if you communicate with any webservices you're still vulnerable.
As example. If you nowadays put a Windows XP machine live on the internet with a public IP, it will be compromised within minutes.
So yeah. Good call switching to Mint, but please don't use unpatched Windows.
That's a tough question and I don't really have am answer.
But if it's work related I'd look into finding a Windows SysAdmin course somewhere and ask my employer to pay for it, since it helps with your work.
A cheaper alternative would be online courses. I found Udemy quite helpful in that regard.
Another possibility is Microsoft Learn, which offers basic to professional "Learning paths" you can do on your own time. There's also a SysAdmin certification available if I recall correctly.
Edit, since I just reread your post: Microsoft Learn is almost completely about Azure. So you should really take a look at it.
Everyone that thinks self hosting E-Mail is easy, I urge you to run your own mailserver and see how many mails actually reach their targets.
Your mailserver won't be trusted by anyone, which makes your email always be delivered as spam, if they don't get blocked outright.
Otherwise this scoring system seems to be quite alright. Even though it could use some more detail and citing some sources for the numbers would be great.
