Here’s the commit in TI’s pru software package where they document some of the INT changes: am335x: Port to Linux 5.10 - pru-software-support-package/pru-software-support-package - The PRU Software Support Package
Basically as you found out, 4.19.x, 5.4.x, and 5.10.x remoteproc’s are not compatible
Regards,