Does the CPU implement the zicsr (control and status register access) extension? The instructions I've got are csrr, csrrw (from FreeRTOS).
I was expecting the Technical Reference Manual to mention zicsr; however, it does go into considerable detail about the CSR features of the processor, so I have considerable confidence.
Also, come to think, the IDF package obtainable from Espressif includes FreeRTOS ...