Unable to domain join in SMB settings

I have two unraid machines that I've recently built and I can't get either to join the domain.
I've been through pretty much every post both here and elsewhere online that I can find on the topic. I'm now multiple hours / days down, £90 in the hole for 2 starter licences and no further forward. . . I'm posting here as a last ditch attempt before I cut my losses and go back to Ubuntu / TrueNAS / Microsoft Server.

Environment:

Unraid 1: HP Micro Gen 8, 4x3TB SATA HDD + 1x250GB SATA SSD

Unraid 2: Dell R420 (controller flashed to IT mode) 4x6TB SAS + 2x1TB NVME

Domain Controllers are Server 2025 with minimal customization.

IP addresses are reserved for the unraid servers and static for the DCs.

DNS server on the unraid machines is set to the IP address of the primary DC.

These are the excerpts from the log:
Aug 14 01:31:33 ASG-UR-HPMSG8-1 emhttpd: shcmd (6324): /usr/local/emhttp/webGui/scripts/update_access

Aug 14 01:31:33 ASG-UR-HPMSG8-1 emhttpd: Stopping services...

Aug 14 01:31:34 ASG-UR-HPMSG8-1 emhttpd: shcmd (6329): /etc/rc.d/rc.samba stop

Aug 14 01:31:34 ASG-UR-HPMSG8-1 rc.samba: Stopping Samba server daemon...

Aug 14 01:31:34 ASG-UR-HPMSG8-1 rc.samba: killall --ns 1872983 smbd nmbd wsdd2 winbindd

Aug 14 01:31:34 ASG-UR-HPMSG8-1 wsdd2[1871652]: 'Terminated' signal received.

Aug 14 01:31:34 ASG-UR-HPMSG8-1 wsdd2[1871652]: terminating.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: Samba server daemon... Stopped.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 emhttpd: shcmd (6330): rm -f /etc/avahi/services/smb.service

Aug 14 01:31:35 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Files changed, reloading.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Service group file /services/smb.service vanished, removing services.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 emhttpd: Starting services...

Aug 14 01:31:35 ASG-UR-HPMSG8-1 emhttpd: shcmd (6335): /etc/rc.d/rc.samba start

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: Starting Samba server daemon...

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: /usr/sbin/smbd -D

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: /usr/sbin/wsdd2 -d -4

Aug 14 01:31:35 ASG-UR-HPMSG8-1 wsdd2[1873071]: starting.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: /usr/sbin/winbindd -D

Aug 14 01:31:35 ASG-UR-HPMSG8-1 winbindd[1873075]: [2025/08/14 01:31:35.765268, 0, traceid=1] ../../source3/winbindd/winbindd_util.c:1233(init_domain_list)

Aug 14 01:31:35 ASG-UR-HPMSG8-1 winbindd[1873075]: Could not fetch our SID - did we join?

Aug 14 01:31:35 ASG-UR-HPMSG8-1 winbindd[1873075]: [2025/08/14 01:31:35.765324, 0, traceid=1] ../../source3/winbindd/winbindd.c:1175(winbindd_register_handlers)

Aug 14 01:31:35 ASG-UR-HPMSG8-1 winbindd[1873075]: unable to initialize domain list

Aug 14 01:31:35 ASG-UR-HPMSG8-1 rc.samba: Samba server daemon... Started.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 emhttpd: shcmd (6336): cp /tmp/emhttp/smb.service /etc/avahi/services/smb.service

Aug 14 01:31:35 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Files changed, reloading.

Aug 14 01:31:35 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Loading service file /services/smb.service.

Aug 14 01:31:36 ASG-UR-HPMSG8-1 emhttpd: shcmd (6340): /etc/rc.d/rc.avahidaemon reload

Aug 14 01:31:36 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Got SIGHUP, reloading.

Aug 14 01:31:36 ASG-UR-HPMSG8-1 avahi-daemon[1869494]: Service "ASG-UR-HPMSG8-1" (/services/smb.service) successfully established.

Things I've tried:
Assessing the domain health - couldn't find any issues

Disabling SMB entirely, then trying again

Rebooting the machine

Using different user accounts

Checked the logs on the domain controllers: Nothing there

Thoughts:

Samba and Kerberos issue? Not sure how I'd diagnose.

I'm by no means a Linux expert, but I know someone who is. . . If there are other things to try, I'm all ears.

Thanks in advance.