“Note that you cannot use the built-in Channel Strip when the sampler rate is set to 176.4kHz or 192kHz.”
This is per page 19 of “UR-RT2_OperationManual.pdf” (i.e. “UR-RT4 UR-RT2 USB AUDIO INTERFACE EN Operation Manual” Manual Development Group ©2018 Yamaha Corporation Published 11/2018 YJTT-BO)
It is not reasonable to sell a 192 kHz audio interface and expect customers to not use it in a 192 kHz mode.
Why should customers discover this short-coming only after sifting through nineteen pages of user guide and after spending $350.00 USD for the device. This is not an over-sight. It’s a disservice.
If it’s any consolation, another USB interface company which manufactures red shell cased devices engages in similar behavior. Accessing the built-in audio interface mixer of company ‘F’'s device while in 192 kHz mode, makes impossible the modification of settings. The I/F must be operating at less that 192 kHz for that to be possible. Information about the limitation is also documented in company 'F’s manual. The limitation lessens with models of increased ports.