If you're running an older version of Windows 10 with Avast or AVG antivirus software, you'll want to hold off on something newer. Microsoft has added a known issue to its Windows 10 Health Dashboard for both version 1903 and version 1909, citing only compatibility issues with the two AV apps.
Right now, there's a hold on installing the two versions of Windows 10, so you won't even get them offered to you through Windows Update. You might be able to use the Media Creation Tool, so there's a note with Microsoft recommending that you don't so that.
The known issue is listed as Mitigated External. That means that it's not something that's going to be fixed in Windows 10. Instead, it's up to the software vendors to fix their apps. The good news is that updates are available, according to support documents from AVG and Avast. You'll want to make sure that you're not on version 19.5 or earlier.
Also be aware that even if you upgrade your antivirus software, the block from upgrading Windows 10 will not be removed. This is typical behavior from Microsoft, as it usually provides a fair amount of time to allow all users to upgrade their AV software before lifting the block.