BillDH2k

@Baio77  It turned out to be a simple fix. The culpit was that GPIO device in the unit #2 was not enabled by the generic "SSDT-GPI0.aml" patch used in my EFI. I had to use a different method, by setting GPEN =1, to enable it (as explained in the OpenCore guide, for my particular case). Also, I updated to the latest woodooI2C.kext. Now the touchpad worked!
 
Here is the updated SSDT-GPIO.aml, only works on unit #2 (it's BIOS ACPI code will enable GPIO if GPEN =1):
/* SSDT-GPIO.aml */ DefinitionBlock ("", "SSDT", 2, "DRTNIA", "GPI0", 0x00000000) {     External (GPEN, FieldUnitObj)     If (_OSI ("Darwin"))     {         \GPEN = One     } }
For comparison, here is the generic patch, which works on unit #1, not unit #2 (#1's BIOS is different. Not 100% sure caused by the version difference, or hardware difference):
DefinitionBlock ("", "SSDT", 2, "hack", "GPI0", 0x00000000) {     External (_SB_.PCI0.GPI0, DeviceObj)     Scope (_SB.PCI0.GPI0)     {         Method (_STA, 0, NotSerialized)  // _STA: Status         {             Return (0x0F)         }     } }  
@Baio77: The AlpsHID kext also worked, but GPIO must be enabled first.

1. Download the appropriate version from the Releases and extract the zip file.
Let’s assume that you downloaded “ALCPlugFix-Swift-RELEASE-1.5.zip” to download folder, and extracted the zip file in the same place (by double-clicking). You would have a new folder “ALCPlugFix-Swift-RELEASE-1.5” created. Right-Mouse-Click on the new folder icon -> Services -> New Terminal at Folder.  A new terminal window would be opened at the current folder path: /Users/YOURNAME/Downloads/ALCPlugFix-Swift-RELEASE-1.5  (You can type “pwd” to verify it)
 
2. Copy the edited sample.plist file (in this case: ALC295-DELL7400.plist) to somewhere safe.
I placed it in “Monterey HD\users\shared”, where Monterey HD is the name for my macOS drive. You may have a different name.
 
3. At the terminal (opened in step 1), type: ./install.sh
Follow the instruction. When it asked for .plist file, drag “ALC295-DELL7400.plist” icon to the terminal, from the location you stored in step 2 above (in my case, it is from “Monterey HD\users\shared\”).
 
You may encounter message like "ALCPlugFix is from unknown source” (1st time install) , just ignore it. After install is completed, go to folder: /usr/local/bin  (this is where ALCPlugFix is installed).  Right-Mouse-Click on ALCPlugFix icon -> Open, then Open again to allow it to run. This would give it the permission to run.
 
Add "alcverbs=1 alcid=77" to the boot args.  Reboot.