Can GLI Comet allow my laptop to control a device without needing a network connection?

That seems to be what NanoKVM-USB does. But GLI Comet seems to be KVM-over-IP?

I use Comet in remote field by plug the ethernet it expects to the laptop. Both will set up the link local IP and accessible in browser without internet

You might be able to use something like usbipd to forward the USB port from your target machine?

Different use-cases. The Sipeed product comparable to the GL-RM1 is the NanoKVM Cube. Comparable to the GL-RM10 is the NanoKVM Pro (Desk).

(Of course you could use the Cube on a crash cart, too. Just like you can use the butt of a screwdriver to hammer a nail.)