@Yoann same issue here. Clean install of Windows Server 2019 latest build, install .NET Framework offline installer 4.8, reboot and boom. Many native control panels, like Server Manager, requesting some 4.0.... version of .NET framework instead, failing to load.
I had the same issue and received zero help or support from Microsoft. Dell support googled and read back to me everything I had googled and tried already. Importing the above registry information fixed it without a reboot.
@DavidSherrill This is the exact fix! For us, our RMM tool stopped working on a server 2019 standard server. It's services wouldn't start. Event Viewer complained about .net. Also server manager wouldn't open with the exact message you mentioned. Applying this fixed it all. thanks!!
YOU ARE AN ABSOLUTE LEGEND! THANK YOU! THIS IS THE ONLY SOLUTION THAT WORKED! Every other solution I've googled of this problem has been some variation of "turn net framework on/off in the "turn windows features on or off" app" or "reinstall the newest version of .net" or "did you try restarting your computer?" (OF COURSE I TRIED RESTARTING MY COMPUTER!! DO THEY THINK I'M AN INFANT??)
Please excuse my novice status displayed in this question, but does one simply copy/paste the text in your registry update file, and does the resulting text file require the line number entries as displayed in your post?