i need to build 5g router with RBM11G did it support 5g modules ?
RBM11G supports mini-PCIe card. In theory a R11e-5HacD a/n/ac wireless card should be just fine. There are other variants (single chain a/n, dual chain a/n variant, 2.4/5 a/b/g/n dual band, …), just look at list of interface devices (page lists also SFP modules, don’t get distracted by those, scroll down and you’ll find some wireless cards).
what i meant is 5g cellular modules like quectel 5g models ,
Well… 5G cellular is wild wild west on MT for now. I don’t think there are any officially supported 5G modems at this time. Some may work but they may stop working with any ROS upgrade …