I am building also a 486 retro system. After checking many forums, also at this site, i found the best motherboard is the Biostar MB8433-UUD. They only have problems with the Dallas chip. However somewhere i have seen there is a hack for it and possible to solder a battery on it.
Further I will add an Intel 486dx4 100mhz CPU, 32MB SIMM memory, Matrox Millenium I 4MB VGA, Sound Blaster awe 32, combined with DOS and Windows 3.1. I also found a Creative Quad speed CD reeder and 5.25" floppy drive from Panasonic. These all will go into a modern house, like Fractal Design R6, but I did not yet decided at this point.

So something like this guy has made here:
https://m.youtube.com/watch?v=YHIVGxNnkbA

Just my 486 will be even better 😀. I careful not to choose newer hardware than 1995. I think that was the last year when 486 was still considered as serius machine.

Hope it helps you!

I have found out that it is really more trouble than it is worth trying to build a 486 computer with todays used parts.
It's hard to find good parts and it is a gamble to buy used parts.
It is much easier, reliable and less expensive to build a DOS computer with modern parts like many You-tubers have mentioned.
A Super Socket-7 Mother board or a Slot-1 BX-440 or BX-443 Motherboard with Pentium-3 500mhz will do just fine.
They have a NEWer bios that can support larger hard-drives and you can configure the bios to slow down the CPU performance for playing old DOS games.

https://www.youtube.com/watch?v=9CgisEFObjA&t=1363s

486 parts are really beginning to get expensive these days. Yes that is true. If you are thinking of doing a "phils 4-in-1" SS7 multiplatform solution. Then I am afraid that you will use way more money, than a 486 these days.

Unless you get something donated, or you are extremely lucky at a local sale/flea market. A gigabyte GA-5AX are near impossible to find, and when they do pop up, they cost at least the same as a 486-board + VLB-Vga + CPU. And that is for the SS7 board alone.

A common socket 7 motherboard can be an acceptable substitute, especially with a PMMX CPU.

I’d argue even a better solution, Triton chipsets are very solid and you have great setmul support for spead flexibility. My main system is a Pentium MMX 233 and I wouldn’t swap it for anything else as a main dos system even though I own pretty much all the other setups including one of the best SS7 motherboards ever made.