Using SerDes with Jetson Xavier AGX
From your list GMSL is definitely best solution.
GMSL used several self-driving car equipment's vendors.
E.g. Maxim Integrated has good GMSL product portfolio.

LVDS is also considerable solution (not only from Thine, most company provide LVDS serdes).

My doubt about multiplexing 9x video streams w/o glue. Tiny (or middle) FPGA would be solve this issue. If we talking about using FPGA, we also might consider to use TMDS connection to cameras (although GMSL stay still #1 in reliability for industrial application).