Support for PCI-E bifurcation on consumer motherboards was really good for a while when PCI-E 4.0 first came out, however it has since regressed again.
Not many motherboards in the latest gen can do a proper x8+x4+x4 split. They may claim to support it but you run into weird issues has to spend weeks waiting for a bios fix. Or sometimes the support might be there but it is so poorly explained in the manual that I had to actually test it on hand to make sure that I was reading it correctly.
To be fair, HEDT motherboards are not immune to this type of stupidity. However they do manage to get over these issues with the sheer number of lanes.
Not many motherboards in the latest gen can do a proper x8+x4+x4 split. They may claim to support it but you run into weird issues has to spend weeks waiting for a bios fix. Or sometimes the support might be there but it is so poorly explained in the manual that I had to actually test it on hand to make sure that I was reading it correctly.
To be fair, HEDT motherboards are not immune to this type of stupidity. However they do manage to get over these issues with the sheer number of lanes.