15-STABLE: dhclient fails on em0 (Lenovo T580)

I recently switched from FreeBSD 14-STABLE to 15-STABLE (after branching of 16-CURRENT)
on my working laptop, physically a Lenovo T580. Its LAN NIC FreeBSD recognizes as em0
(see below). System is at: 15.0-STABLE #16 stable/15-n281349-b903f27e171b: Fri Nov 28
05:20:32 CET 2025 amd64. Kernel config: GENERIC.
Configuration has been setup and renewed acording to changes, consider the system as a
fresh install.

Problem: em0 never gets an IPv4 via DHCP on startup (init process via rc.conf).

Configured in /etc/src.conf:
[... WORKAROUND ...]
netwait_enable="NO"
netwait_if="em0"
[...]

and on a regular basis:
[...]
ifconfig_em0="DHCP"
ifconfig_em0_ipv6="inet6 accept_rtadv -ifdisabled nud -no_radr auto_linklocal"
[...]

Very strange: after a final boot up, its very easy to require and achive an IPv4 with 

dhclient em0

I'm out of ideas ...





====
pciconf:
[...]
em0@pci0:0:31:6:        class=0x020000 rev=0x21 hdr=0x00 vendor=0x8086 device=0x15d8
subvendor=0x17aa subdevice=0x225a vendor     = 'Intel Corporation'
    device     = 'Ethernet Connection (4) I219-V'
    class      = network
    subclass   = ethernet
    bar   [10] = type Memory, range 32, base 0xe8200000, size 131072, enabled
    cap 01[c8] = powerspec 3  supports D0 D3  current D0
    cap 05[d0] = MSI supports 1 message, 64 bit enabled with 1 message
    cap 13[e0] = PCI Advanced Features: FLR TP

[...]

dmesg:
ichsmb0: <Intel Sunrise Point-LP SMBus controller> port 0xefa0-0xefbf mem
0xe8253000-0xe82530ff at device 31.4 on pci0 em0: <Intel(R) I219-V SPT(4)> mem
0xe8200000-0xe821ffff at device 31.6 on pci0 em0: EEPROM V0.1-3
em0: Using 1024 TX descriptors and 1024 RX descriptors
em0: Using an MSI interrupt
em0: Ethernet address: 48:2a:e3:3a:cf:52
em0: netmap queues/slots: TX 1/1024, RX 1/1024