I am troubleshooting slow boot times with KDE, and it seems that NetworkManager is taking a few seconds to boot. I found these warnings from kernelring buffer's journal:

Oct 06 22:08:59 archlinux kernel: r8169 0000:08:00.0: Direct firmware load for rtl_nic/rtl8168h-2.fw failed with error -2
Oct 06 22:08:59 archlinux kernel: r8169 0000:08:00.0: Unable to load firmware rtl_nic/rtl8168h-2.fw (-2)
Oct 06 22:08:59 archlinux kernel: Generic FE-GE Realtek PHY r8169-0-800:00: attached PHY driver (mii_bus:phy_addr=r8169-0-800:00, irq=MAC)
Oct 06 22:09:00 archlinux kernel: r8169 0000:08:00.0 enp8s0: Link is Down
Oct 06 22:09:03 archlinux kernel: r8169 0000:08:00.0 enp8s0: Link is Up - 1Gbps/Full - flow control rx/tx

lspci | grep Ethernet
08:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)

Ultimately the card works, but the kernel spends some seconds trying to get it working, and it my be delaying the boot. I've tried using the 8168 module and adding iommu=soft to kernel parameters, neither worked. Does anyone else here has had this problem ?