I have 2x PCIe X16 and 1x PCIe 1x slots that are not being used. Given that Linux has extensive hardware support, there are probably users with interesting PCI card usages
Aside from traditional usages like network/wireless/bluetooth/sound that can easily be used as USB (or built in advanced sound support in the MOBO), what are your use cases with PCIe?
How have you handled power delivery for 2 GPUs? Are you using two PSUs or one beefy one?
A molex to PCIe adapter with an 850w power supply. I only have like 10 watts of headroom but usually only one gpu is running at a time so it works fine. I would have bought a better one but my dad accidentally bought 2 for another project so he had an extra one and it works fine.