Thread moved to https://forum.xda-developers.com/galaxy-s9/samsung-galaxy-s9--s9-cross-device-development/twrp-exynos-t3763464.
In theory you can, but so far no one including myself has been able to root from this.
@jesec if this twrp is becoming the official one I suggest you to include some of my features/fixes as for example img flash to specific partitions, OTG fix and more (also people on the s9+ thread reported that usb wasn't working), check my device tree here.
Have a nice day!
Will we see a kernel of yours ?After following the instructions exactly in the OP, I flashed SuperSU v2.82-SR5-20171001224502. My S9 is rooted and everything is working great!
(NOTE to North Americans: Don't get your hopes up, although I am in Canada, I have the Exynos version SM-G960F)