Mark:
The second link you posted (https://osxlatitude.com/forums/topic/13071-dell-latitude-e7440-catalina-10154) is the one i used to build a new e7440 two days ago. The guide was great, and the ONLY issue i had was to make sure you format the drive in the dell correctly, not as Mac OS Extended but as APFS. Make sure your BIOS is a28.
Follow Hervé's bios set up, and the EFI folder provided by trognaz seemed to work perfectly (though I wouldn't mind someone to confirm it's all the latest drivers).
I was pretty impressed with the specs: it was showing on Geekbench with just about the same speed as my macbook pro (2016) single core. My macbook Pro has 4 cores, so it would hit x2 the speed of the e7440, but only on programs that can take advantage of them.
Hervé/Jake:
Can you recommend a Broadcom? I screwed up and got a DW1560 which turned out to be the wrong connector. (need Mini PCI). Any suggestions would be awesome.