Like as dotnet/dotnet-docker#1537
but I have same error on CenOS 8 (not Docker) on standalone machine.
Clean new CentOS 8 with latest updates on 23 dec 2020.
in console:

sudo dnf install aspnetcore-runtime-3.1 - OK

dotnet - OK (shows using manual)

dotnet --info - error:
A fatal error occurred, the folder [/usr/share/dotnet/host/fxr] does not contain any version-numbered child folders

dotnet --list-runtimes - error:
A fatal error occurred, the folder [/usr/share/dotnet/host/fxr] does not contain any version-numbered child folders

dotnet *.dll - error:
A fatal error occurred, the folder [/usr/share/dotnet/host/fxr] does not contain any version-numbered child folders

the folder /usr/share/dotnet/host/fxr is really empty. Trying to install SDK - no effect