This should work without any hacks when the IGPU is configured in the way macOS expects when a discrete card is also in use as the main display.
What works in previous macOS versions or for using the IGPU as the primary display device (e.g. Clover injecting 'InjectIntel' device properties and ig-platform-id with connected devices) may not work in the present scenario. If it works you can see these green entries under IntelAccelerator, wrong configuration then no IntelAccelerator and no JPEG decoding.
View attachment 353736
These patches or your motherboard-specific ones probably help.
Code:
<dict>
<key>Comment</key>
<string>Rename GFX0 to IGPU</string>
<key>Find</key>
<data>R0ZYMA==</data>
<key>Replace</key>
<data>SUdQVQ==</data>
</dict>
<dict>
<key>Comment</key>
<string>Rename HECI to IMEI</string>
<key>Find</key>
<data>TUVJXw==</data>
<key>Replace</key>
<data>SU1FSQ==</data>
</dict>
<dict>
<key>Comment</key>
<string>Rename PEGP to GFX0</string>
<key>Find</key>
<data>UEVHUA==</data>
<key>Replace</key>
<data>R0ZYMA==</data>
</dict>
With those and no Intel graphics injection, for me at least, Preview and Quicklook work as expected.