New BR 200 need to clone MAC

A little background. Few years back I subscribed to ATT Fiber. ATT provides the modem but is horrible from management and wifi aspect. They provide either Pace AC5268 or Arris BGW210. Some people put the Pace or the Arris in pass through mode but that is not really pass through. There is also the dumb switch method or extract certs typically from the BGW210 - not doing the certs extract.Plenty of posts about this at dslreports.

Little background: For the dumb switch method power off all then power on the ONT only. Let ONT come up and after few minutes connect the ethernet port on the ONT to one of the dumb switch port. Give it a few minutes then from another port on the switch plug in to ATT WAN RG/modem port. Give it few minutes then unplug the ATT WAN cable and plug in the same cable in the WAN port router of choice and manually add the MAC of the ATT modem in the router of choice.

Sounds complicated but is not basically the ONT will be talking to the dumb switch at all times and from the dumb switch connect the choice router that now has the cloned ATT MAC.

However since the BR200 does not have a manual MAC clone I am not sure how is done.

There is no PC involved in this except manually adding the MAC of the ATT modem into the chosen router or in this case the BR 200. There is no PC that the modem controls or trust or needs. PC is striclty one time use to add the ATT MAC in the router of choice.

For the post above "or for example your old router while connecting the computer to control it t the old router LAN" i am not unerstanding this. Does the PC needs to be connected to the ATT router ? if so where does the BR200 needs to be connect also to the ATT router ? how would the BR 200 get the MAC of the ATT router ? is there  way to know or check ?

Reason I went with the BR200 is that consumer wifi routers are a disaster for the most part either due to horrible wifi and instability or non existent security updates. Planning to use a Ruckus AP with the BR200.

However need to be able to clone the MAC first, if that is not possible unfortunatley as much as I like the BR200 I would need to return it.

Thanks for the help.