Gateway Downlink Frequencies for Class C Devices

the question is not specifically the implementation of TTN community network on but on lorawan specs in general.

I intend to build a network with one or more gateways in a private lorawan network. all devices are class C devices. is it possible for different devices to listen to different RX2 frequencies class C operation? and of course, the gateway will use different downlink frequencies for different devices (to reiterate, this is not for class A operation).

the intention is to maximize all available channels while maintaining duty cycle per channel.

That depends on the backend software you will be using. Keep in mind TTN uses an RX2 frequency (in EU) in the 10% band and all other frequencies are in 1%, so switching frequencies might reduce in stead of increase available airtime.
AFAIK TTN V3 does not support this.