Reboot seems to have fixed it and made it visible. Leaving this post up so others have all the commands in one place.

[14:15 cloud ~]# ethtool -i eth5
driver: i40e
version: 2.26.8
firmware-version: 9.50 0x8000f255 23.0.8
expansion-rom-version:
bus-info: 0000:5e:00.1
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: yes

I am trying to get an Intel X710-DA2 working with a fresh load of 8.3.

This is on a Dell R640 server - the bios and idrac see the X710 in slot 2.

lspci and modprobe see the card - but ifconfig and ethtools does not.

I loaded the alt drivers: yum install intel-i40e-alt --enablerepo=xcp-ng-testing

rmmod i40e
modprobe i40e

lspci sees the card.

[12:58 cloud extra]# lspci |grep 710
5e:00.0 Ethernet controller: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ (rev 01)
5e:00.1 Ethernet controller: Intel Corporation Ethernet Controller X710 for 10GbE SFP+ (rev 01)

modinfo i40e

[13:00 cloud extra]# modinfo i40e
filename:       /lib/modules/4.19.0+1/override/i40e.ko
version:        2.26.8
license:        GPL
description:    Intel(R) 40-10 Gigabit Ethernet Connection Network Driver
author:         Intel Corporation, <e1000-devel@lists.sourceforge.net>
srcversion:     666622D0DB1EB24725D7453
alias:          pci:v00008086d0000158Bsv*sd*bc*sc*i*
alias:          pci:v00008086d0000158Asv*sd*bc*sc*i*
alias:          pci:v00008086d00000DDAsv*sd*bc*sc*i*
alias:          pci:v00008086d000037D3sv*sd*bc*sc*i*
alias:          pci:v00008086d000037D2sv*sd*bc*sc*i*
alias:          pci:v00008086d000037D1sv*sd*bc*sc*i*
alias:          pci:v00008086d000037D0sv*sd*bc*sc*i*
alias:          pci:v00008086d000037CFsv*sd*bc*sc*i*
alias:          pci:v00008086d000037CEsv*sd*bc*sc*i*
alias:          pci:v00008086d00000D58sv*sd*bc*sc*i*
alias:          pci:v00008086d00000CF8sv*sd*bc*sc*i*
alias:          pci:v00008086d00001588sv*sd*bc*sc*i*
alias:          pci:v00008086d00001587sv*sd*bc*sc*i*
alias:          pci:v00008086d0000104Fsv*sd*bc*sc*i*
alias:          pci:v00008086d0000104Esv*sd*bc*sc*i*
alias:          pci:v00008086d000015FFsv*sd*bc*sc*i*
alias:          pci:v00008086d00001589sv*sd*bc*sc*i*
alias:          pci:v00008086d00001586sv*sd*bc*sc*i*
alias:          pci:v00008086d0000101Fsv*sd*bc*sc*i*
alias:          pci:v00008086d00000DD2sv*sd*bc*sc*i*
alias:          pci:v00008086d00001585sv*sd*bc*sc*i*
alias:          pci:v00008086d00001584sv*sd*bc*sc*i*
alias:          pci:v00008086d00001583sv*sd*bc*sc*i*
alias:          pci:v00008086d00001581sv*sd*bc*sc*i*
alias:          pci:v00008086d00001580sv*sd*bc*sc*i*
alias:          pci:v00008086d00001574sv*sd*bc*sc*i*
alias:          pci:v00008086d00001572sv*sd*bc*sc*i*
depends:
retpoline:      Y
name:           i40e
vermagic:       4.19.0+1 SMP mod_unload modversions
parm:           debug:Debug level (0=none,...,16=all) (int)
parm:           l4mode:L4 cloud filter mode: 0=UDP,1=TCP,2=Both,-1=Disabled(default) (int)
parm:           enable_fw_lldp:Don't disable FW-LLDP during NIC init (bool)

Not sure why I can't find an ethX for the card under ifconfig or ethtools.

@olivierlambert @prilly Just loaded the XCP-ng 8.0 successfully on a Dell C6100 with 2 x L5630.

No errors during install, and boots up just fine for use.

@Prilly I installed Citrix Hypervisor 8.0 on my Dell C6100 which is running L5630 CPU and it booted just fine.