Cool, but nor the Windows nor Android Bios'es are made for InsydeQ2S. Lenovo uses a custom made BIOS...
Folks, Lenovo used on purpose different bios'es. The Android Version will never understand ACPI, UEFI, Bitlock etc... it's cropped EEPROM is just not meant for it. I know it's a frustration, but it won't happen. The Windows Version will "maybe" be able to load some kind of x86 Android, but what about display, halo, wifi, anypen, wacom, dolby etc drivers?
i don't have device in my hands now
but i have a little hope

at least we can boot windows or android from USB/microSD
hmm
for windows version it must be easy
we can keep windows on primary disk
and install android on external drive
* :|||| then how this s**t can boot it?
hmm, we need to disable secure boot
then add grub to bcd with easybcd
* :\ android need system/boot/data/cache... !!
yep, we need to partition usb drive like official android disk
same sizes for system, cache, ...
not userdata
then we need to edit ramdisk
we need to edit fstab(and init.r2_cht_ffd.rc) to mount system and other partitions from /dev/sdb(c) [instead of /dev/block/by-name/]
* what about other partitions like keymaster?
i'm not sure it's needed but we can symlink it on init scripts
but for android version i'm not sure what i have to do

first i downloaded android firmware zip and there was file called "bootloader"
Code:
/Volumes/ExFAT 1/YB1-X90L_USR_S000155_1609272258_WW06_BP_ROW-flashfiles/bootloader: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "mkfs.fat", sectors/cluster 4, root entries 512, Media descriptor 0xf8, sectors/FAT 200, sectors/track 32, heads 64, sectors 204800 (volumes > 32 MB) , serial number 0x786ce839, label: "ANDROIDIA ", FAT (16 bit)
so it's fat image
and i was able to mount it
BINGO
volume label is ANDROIDIA just like what i saw in chawe boot option photos in OP guide
well on bootloader i can see \EFI\BOOT\bootx64.efi
:good: :good: :good:
now i'm sure android version yoga can also boot (any)efi file
* but who dare to touch it?
noone, we have tool called efidroid :
https://forum.xda-developers.com/android/software-hacking/efidroid-t3447466
this guy can boot efi files for us
someone have to port efidroid for yoga (thats why i asked for device tree on TWRP thread)
now we need windows boot manager efi files (uefi boot partition) and windows system files to boot windows
ok, i'm not sure how to install windows on usb at this stage
but for example we can boot windows setup usb
(we need to find a way)
like install windows by virtualbox with PC on USB, then try to boot it on yoga (not sure)
or took backup of windows version and restore on USB :\
my friend wants to buy windows version (right now we have shipping problem from amazon) and i will try to install android on it
then if anyone wants to work, i hope can help