.NET framework 3.5 not downloading

No idea. I couldn't install it. Apparently they had a cutoff for the TPM requirement bypass which I couldn't get through. For me, it fortunately didn't install. But if you want Win11, good luck.

I didn't want it and by switching to Dev via the registry, it started downloading 11 instead of the latest 10. I applied a license for 10 so I'm going to end up sticking here until Parallels gets TPM 2 running on it.... If ARM64 gets the 21h2 release outside of beta, then I'll have a full licensed version that I can use until TPM 2 comes in Parallels.

 

OK, I just bit the bullet and did this UUPDump. Got a 21390 ISO which I saved from the desktop and it downloaded the .NET 3.5
This is excellent. Thank you. Everything seems to be working fine still. Nice.

 

Try running the .NET Framework Repair Tool, after scanning fix the internal glitches that causing the problem .net framework 3.5 is not working. Moreover, you can also try installing the .NET Framework 3.5 utilizing Windows Features.
Hope this works for you but if then read the article to find out more possible fixes to solve the .Net framework 3.5 installation issues
Source: https://www.pcerror-fix.com/net-framework-3-5-installation-error-0x800f0950