FYI, “Linux for Tegra” (“L4T”) is a purely Ubuntu system with hardware drivers added by NVIDIA. Other than the drivers it is Ubuntu. Anything the Linux kernel can do on Ubuntu the Jetson can do. ext4 happens to be the default, but if there are other file system types the kernel can be configured for, then likely the Jetson can as well under L4T (you’d just build the kernel with the features you are interested in, e.g., a file system…I know nothing about UBIFS though…perhaps there are user space tools required in addition to the kernel requirements).
Looking at the “/proc/config.gz” of a running TX2 under L4T R28.2 (the most recent release) I see this for the kernel config:
# CONFIG_UBIFS_FS is not set
So far as kernel support goes you could probably just rebuild the kernel or build and add a module.