It just got quite usable! GenI2C solved the problem by compiling a patch for TPL1 to operate in polling mode. I put that into the config.list and sleep started working as needed, even overnight. Now TPD0 / 9d60 is the touchscreen and that seems to have issues with bus timeouts.
kernel: (kernel) VoodooI2CControllerDriver::pci8086,9d60 Timeout waiting for bus to accept transfer request
log messages are the sign. It still works, but going to sleep takes some time, maybe 15sec longer. So I created a SSDT to deactivate the touchscreen and going to sleep became faster. Quite fast actually. If you want to keep using the touchscreen you'll have to live with some 10-15 sec delay when going to sleep. Then, just delete the TPD0-OFF-YOGA920.aml file from patched. There should be no other issues.
Change log to the last version:
- TPL1 (touchpad) now operates in polling mode. Feels a bit smoother, all gestures I tried work. Unfortunately typical for Windows-oriented laptops are their small touchpads. There's so much space, why are the trackpads so damn small?
- Added .aml and a patch to config.plist
- Touchscreen deactivated to go to sleep faster. For keeping it just delete the TPD0-OFF-YOGA920.aml file.
- Chime at boot works
This is the EFI that should provide very decent funcionality, here it's Catalina with all patches. Just create yourself a new serial number and have fun!