Persee bricked after disabling lightdm

You can use rkflashkit to read the “linuxroot” partition to your Linux computer, mount the .img, modify it to undo the systemctl command, and flash the linuxroot back in. Alternatively if you don’t care about the data being lost, just flash the Persee again using the Ubuntu images from Orbbec. I wrote some instructions for the flashing stuff here.