There are still some mainboards with PCI available, you only have to search for that using a suitable platform.
Here is an example for a quite recent board from Supermicro:
https://geizhals.de/?cat=mbp4_1700& … TX%7E489_1
I can recommend getting the Supermicro boards with an "-F" at the end of the name.
As Mainboard with DUAL-BIOS are rare.
This means they have a web-based management interface to so called "IPMI", which makes remote administration possible.
It is even possible to flash the BIOS from the IPMI. Especially this is a life safer just in case a flashing failed.
Other systems with only one BIOS you would need to send back to the factory for repair (time, costs, ..).
By this, you have the chance to flash it again.
I remember there are other systems with PCI slot.
You need simply to go through every CPU type and filter again for PCI ">1"
Maybe also for ATX to get rid of µATX boards.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14