My 20H2 install got trashed, but it's not a big deal. Currently typing this from 2004/20H1 with updates blocked so it's currently nice and creamy. The nice thing about installing everything after 7, it's very easy to have multiple partitions on a drive and you can install different versions of the Windows OS or even the same OS but different builds to different partitions and simply choose which one you want to boot from from the normal bootloader. Mixing non-Windows OSes into it (Linux, Haiku, BSD, etc) needs to chain bootloaders.
To that end, here is a 24-hour link to the iso of 21H1 if anyone wants it. It's going to be the same as 20H1 and 20H2. The big changes won't be till the fall, with "Sun Valley". This iso has one very curious feature in it which surprised me. Legacy edge is in it, and it wasn't in the 20H2 one but I'm not complaining because this is part of why I reinstalled 2004 into this partition.
https://software-download.microsoft.com/pr/Windows10_InsiderPreview_Client_x64_en-us_19043.iso?t=0d811a1f-b78a-4cf9-add0-0ee333cd1ce9&e=1615765496&h=180bdf2332cb28487752f5fdf5171f80
Software update will install the March cumulative update into it, and you will end up with a build # of 19043.867 (844 on install). If your system is fine, don't bother with this iso as there are no changes for a PC.