I have installed OperaGX from this url: https://www.opera.com/gx which gave me installed of 4Mb which is not working. It throws error that I can't install it on my PC.
But if I download from https://www.opera.com/download#opera-gx then it will download a 115mb which will install OperaGX in my system successfully.
Please look into the Download link on https://www.opera.com/gx URL.