MR7500 (M7 Ultra Telstra) not connecting to 5G on Optus – firmware restriction?

Hello everyone,

I have a Netgear Nighthawk M7 Ultra (MR7500) originally branded with Telstra firmware.

Current firmware details:

Firmware Version: NTGX75_10.04.09.00

GUI Version: M7_Telstra_v07.01.47.00

The device is unlocked and paid outright.

I am using an Optus 5G SIM in a full Optus 5G coverage area.

The same SIM connects to 5G immediately when inserted into a 5G mobile phone.

However, in the M7 Ultra it only connects to 4G / 4G+ (never shows 5G or 5G NSA).

Network settings:

Band Region: LTE + 5G NSA

Network Mode: Auto

I would like to know:

Does Telstra firmware restrict 5G connectivity on other carriers such as Optus?

Is there an official global/unbranded firmware available for MR7500?

Has anyone successfully converted a Telstra MR7500 to global firmware?

Any guidance would be appreciated.

Thank you.