Les messages SystemIO range conflicts with OpRegion sont liés à l'ACPI et me semblent sans lien avec le pb de réseau.
L'ACPI et le réseau étant initialisés simultanément.
Sur le kernel 5.4 avec le réseau ok, on a également ces erreurs ACPI. J'ai colorié pour que ce soit plus lisible :
[ 2.938106] ACPI: watchdog: Skipping WDAT on this system because it uses RTC SRAM
[ 2.952029] ACPI Warning: SystemIO range 0x0000000000000428-0x000000000000042F conflicts with OpRegion 0x0000000000000400-0x000000000000047F (\PMIO) (20190816/utaddress-204)
[ 2.975509] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[ 2.992245] ACPI Warning: SystemIO range 0x0000000000000540-0x000000000000054F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20190816/utaddress-204)
[ 2.992331] bnx2: QLogic bnx2 Gigabit Ethernet Driver v2.2.6 (January 29, 2014)
[ 3.019454] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[ 3.040639] bnx2 0000:01:00.0 eth0: Broadcom NetXtreme II BCM5716 1000Base-T (C0) PCI Express found at mem c0000000, IRQ 16, node addr d4:ae:52:ce:c5:c7
[ 3.056877] ACPI Warning: SystemIO range 0x0000000000000530-0x000000000000053F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20190816/utaddress-204)
[ 3.105212] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[ 3.107974] bnx2 0000:01:00.1 eth1: Broadcom NetXtreme II BCM5716 1000Base-T (C0) PCI Express found at mem c2000000, IRQ 17, node addr d4:ae:52:ce:c5:c8
[ 3.125047] ACPI Warning: SystemIO range 0x0000000000000500-0x000000000000052F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20190816/utaddress-204)
[ 3.125050] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[ 3.125051] lpc_ich: Resource conflict(s) found affecting gpio_ich
[ 3.236453] i801_smbus 0000:00:1f.3: SMBus using PCI interrupt
[ 3.247712] ACPI: watchdog: Skipping WDAT on this system because it uses RTC SRAM
[ 3.259068] bnx2 0000:01:00.1 em2: renamed from eth1
[ 3.281286] hidraw: raw HID events driver (C) Jiri Kosina
[ 3.292098] ahci 0000:00:1f.2: version 3.0
[ 3.292312] ahci 0000:00:1f.2: AHCI 0001.0300 32 slots 6 ports 3 Gbps 0x1 impl SATA mode
[ 3.314195] ahci 0000:00:1f.2: flags: 64bit ncq pm led clo pio slum part ems apst
[ 3.336052] scsi host0: ahci
[ 3.347650] scsi host1: ahci
[ 3.352484] bnx2 0000:01:00.0 em1: renamed from eth0