OI 2018.04 medium won't boot in legacy mode on Lenovo X220
Lenovo X220 and perhaps other older ThinkPads have an infamous BIOS bug (which is not fixed even in the most recent BIOS update) where it refuses to boot from GPT disk in legacy boot mode. When the BIOS sees GPT it assumes UEFI. More info here: https://lists.freebsd.org/pipermail/freebsd-current/2015-July/thread.html#56543
With recent changes to the install media (I think https://github.com/OpenIndiana/slim_source/pull/36), the 2018.04 USB medium boots only in UEFI mode. As a result Server & Minimal media are not usable as VGA console is not supported in UEFI, but MATE medium can be booted when SSH server is enabled in bootloader and OS thus boots straight to X.
OmniOS CE, though in the installer, has two types of workarounds to handle this: https://github.com/omniosorg/kayak/blob/master/installer/dialog-install#L322. Only the latter worked for me. Wonder if we should have those workarounds in the installer as well.