I just went through almost all of the identical issues described with a 2012 11in MacBook air. Also I was doing it for the same reason, I want to learn how to support Apple systems so I dived head first.
When I was getting those SSL errors I thought it was because I bent the antenna connectors to the AirPort card! Anyway I pumped my way from Catalina, wiped everything, after 10 tries finally got Mountain Lion on there, used a sketchy torrent to force my way into Yosemite, and almost right away Apple was like "Here, have Catalina back, we pity you".
Now I have partitioned the 125GB ssd in to two halves, one is an APFS cluster running Catalina just fine, and took some tinkering but I'm also dual booting into stripped down Windows 10 on the other half of the SSD(boot camp)
I could not have done this without my Linux live boot friends! Windows Lies! Apple Lies! Linux actually tells you where your harddrives are.
I consider it to have been a positive learning experience. It's already taught me a lot of useful things that I'm applying to my new media heavy all Mac client, with a mix of Intel and M1 devices.