Exchange 2016, owa/auth.owa and error 500

Get-owaVirtualDirectory "\owa (Default Web Site)" | Set-owaVirtualDirectory -FormsAuthentication $true -BasicAuthentication $true -WindowsAuthentication $false
 
Get-ecpVirtualDirectory "\owa (Default Web Site)" | Set-ecpVirtualDirectory -FormsAuthentication $true -BasicAuthentication $true -WindowsAuthentication $false

After executing the above commands, do an IIS reset.

Reference from

https://paweljarosz.wordpress.com/2019/01/03/exchange-2016-owa-auth-owa-and-error-500-on-ecp/