Kernel needs to enable CONFIG_HOTPLUG_PCI_PCIE:
https://cateee.net/lkddb/web-lkddb/HOTPLUG_PCI_PCIE.html
reddit task: https://www.reddit.com/r/SolusProject/comments/78eo8t/kernel_module_for_pcie_hotplug_missing/?st=j95ppewh&sh=2ede7352
Very likely need to enable CONFIG_HOTPLUG_PCI_ACPI too