I don't know if you made progress with the motherboard with socket 4, for my part, I investigated the topic, and there are some things that can create problems, first of all the DALLAS chip, it must be working, if it is defective it can prevent starting, at least that's what I read on the pages I visited.
For the BIOS discussion, it seems that you have to use a bootable floppy, but the biggest problem is that not seeing the main screen, you can't see which BIOS was there (written in the chip), moreover the chip should be soldered, maybe 🤔 disconnecting it is not a big problem, but it looked like a card with BIOS easily available, instead from what I keep reading, it seems a bit complicated, in short I don'm not understanding anything anymore!
In addition, there is also the doubt about which card it really is, to tell you, mine is a Mercury, but maybe it is a Hendrix, or are they the same thing? 😨
Anyway if you want I can try to copy the BIOS of my MB, but it probably won't work, according to what I've read.
AMD 286-16 287-10 4MB HD 45MB VGA 256KB
AMD 386DX-40 Intel 387 8MB HD 81MB VGA 256KB
Cyrix 486DLC-40 IIT387-40 8MB VGA 512KB
AMD 5X86-133 16MB VGA VLB CL5428 2MB and many others
AMD K62+ 550 SOYO 5EMA+ and many others
AST Pentium Pro 200 MHz L2 256KB