@maurice
mine:
macbookair2013mid with ubuntu 20.04.
pixel2 xl 128g with android 9 factory image.
download and install <- all like you did.
format data in twrp first, when everything ready.
flash halium-boot.img.
flash vendor.img.
fastboot boot twrp.img(3.50) then sreen just show twrp logo.never get menus.
install last install commad.
adb reboot.