Getting Linux working on ChromeOS Flex on older devices

I installed ChromeOS Flex on my late 2008 Macbook . Unfortunately I cannot enable Linux mode yet. These threads on reddit (1 and 2 ) that suggest changing ChromeOS Flex to developer mode would fix it. So I added the cros_debug flag to GRUB (efi and syslinux) configuration files and I also checked for the kvm-intel.vmentry_l1d_flush=always flag and it was already present in every single grub config file entry. Still when I try to start termina I get the following:

crosh> vmc start termina --untrusted
Error: operation vm_start failed: bad VM status: VM_STATUS_FAILURE: Host vulnerable against untrusted VM
[ERROR:src/main.rs:184] ERROR: command failed

Next I tried looking up the l1tf vulnerabilities on my laptop and this is what I encountered:

crosh> shell
chronos@localhost / $ cat /sys/devices/system/cpu/vulnerabilities/l1tf
Mitigation: PTE Inversion; VMX: EPT disabled

Edit: I have now also added the kvm-intel.ept=0 too, see bellow:

chronos@localhost / $ cat /proc/cmdline 
BOOT_IMAGE=/syslinux/vmlinuz.A init=/sbin/init boot=local rootwait ro noresume noswap loglevel=7 noinitrd console= kvm-intel.vmentry_l1d_flush=always kvm-intel.ept=0 dm_verity.error_behavior=3 dm_verity.max_bios=-1 dm_verity.dev_wait=1 i915.modeset=1 cros_efi cros_debug root=/dev/dm-0 "dm=1 vroot none ro 1,0 4710400 verity payload=PARTUUID=E09BB354-34E7-5343-B0A2-BB06778C6B78 hashtree=PARTUUID=E09BB354-34E7-5343-B0A2-BB06778C6B78 hashstart=4710400 alg=sha256 root_hexdigest= salt="

I am not sure what the mitigations mean in practical terms, but I wonder if are there any other GRUB flags I could add to overcome the error I am having starting crostini?