I have to thank this great forum. Today I have successfully installed catalina 10.15.5. And I also successfully updated 10.15.6. Apparently, the "Opencore" method is also being actively discussed, but I'm not sure if the I've come to the conclusion that "Clover" has a better track record with less trouble.
Here are the topics I referred to for the installation.
1) Catalina Clover Guide
https://osxlatitude.com/forums/topic/8506-dell-latitude-inspiron-precision-vostro-xps-clover-guide/?tab=comments#comment-94956
Special thanks: JakeLo
2) Wireless cards
https://osxlatitude.com/forums/topic/11138-inventory-of-supportedunsupported-wireless-cards-2-sierra-catalina/?tab=comments# comment-86614
Special thanks: Hervé
Finally, the Latitude's internal card works with the following kext. I just use the TPLINK wireless module.
MacOS will be Arm-based and osxlatitude will be more prolific. I'd like to contribute if I can. The best I can do right now is to donate via Paypal, lol.