@stephenw10 - Ok... So... Bear with me... I just spent about 6 straight hours troubleshooting and didn't really accomplish much.
Upgraded the firmware on the card, that was a breeze. Took about 15 min through UEFI. Here is the new firmware information:
dev.ixl.0.fw_version: fw 9.140.76856 api 1.15 nvm 9.40 etid 8000ed12 oem 1.269.0
Appears to be much newer, and BONUS, it STILL works with 23.09.1.
Long story short, SAME exact symptoms with 24.03.
So, I decided to factory reset the configuration. After the reboot, I manually reassigned the interfaces to be the correct ones for at least my LAN and WAN, manually set the IP address for the LAN and.... NOTHING. I performed a reboot just for giggles, and, wouldn't you know it, it WORKED. And it was repeatable. 3 reboots later and I was confident that it was 'stable'.
I took my backup config (downloaded from the working 23.09.1), loaded it on the GUI, and it... kinda worked after a reboot. The LAN interface came back, and all the other settings came back, but I got an effort for EVERY package that basically said, "Package ABCDEF does not exist in current Netgate pfSense Plus version and it has been removed.", for all 22 of my packages.
I rebooted a couple times, and it again seemed 'stable' on the LAN interface.
I started adding my packages, they all came up and worked no problem... Then I rebooted again... LAN interface was dead again. Reboot 3 more times... still dead. Reboot into the 23.09.1 boot environment, everything is hunky dory again.
So... Maybe it's related to SOMETHING in my configuration related to the packages I have installed?
Here is the list of all 22 packages that I use:
mailreport
iperf
nmap
mtr-nox11
openvpn-client-export
acme
bandwidthd
Cron
Status_Traffic_Totals
syslog-ng
Service_Watchdog
System_Patches
avahi-daemon
arpwatch
pimd
pfBlockerNG
zabbix-agent64
nut
WireGuard
suricata
ntopng
If I had to make a guess, I would suspect that MAYBE it has something to do with either bandwidthd, Status_Traffic_Control, avahi-daemon, or pimd because I believe those actually have the ability to muck with the interfaces at a more substantial level than the rest of the packages. I'm reasonably certain that I never actually got media casting across VLANs to work successfully. so I think I can ditch avahi-daemon and pimd. Might be able to nix the others too, but I'm not actually sure if that's really needed.
I'm willing to share my config privately with support if you think there's something in there that might help.
Back on 23.09.1 for now...