To me this belongs to the more advanced topic so that I do not recommend average people to try it.
Mac Address clone seems to be the tricky part for VSOL GPON ONU as it seems to require some auth key generation from what I read. There are some Chinese websites which seem to provide the guide but you need to register and pay a small amount of money. The website registration may be another issue as it may require mainland China mobile number.
One reference found with Google.
https://www.right.com.cn/FORUM/thread-8305120-1-1.html
If you bought it from Taobao, you may try your luck to contact the seller for help.
Not so sure if the following github page helps or not.
https://github.com/Anime4000/RTL960x
BTW, I have bought the VSOL V2802RH myself (an impulse buy last September at RMB 187) but I have not even opened the box. After I bought it I realized it might not be easy to get SingTel TV working. I might give it a try again if I decide to cancel my SingTel TV. But since I am an SingTel ONT user with 1Gbps plan, not so much motivation to try.
Edit to add: it is said that latest 1.1.8 Firmware updates will allow you to change MAC address by yourself.
https://www.right.com.cn/FORUM/thread-8385162-1-1.html