I managed to bring my NAS back to life.
While still on USB stick (version 13.0-U4), I used this
link to try to configure my network.
In the end I made 2 things using the option "9" from CLI :
vi /boot/loader.conf
+ if_re_load="YES"
This is supposed to load the Realtek NIC's driver at boot
vi /etc/resolv.conf
+ nameserver 8.8.8.8
+ nameserver 8.8.4.4
"ifconfig" stated that everything was fine (but it always was based on screenshots).
I also disconnected then reconnected ethernet cable for what matters.
At that point, ping from Windows was OK and I could access GUI on 192.168.1.101
Then I reloaded the configuration from a save and I salvaged all my samba share as if nothing happened.
I'm still skeptical about the fact that the aforementioned actions really "repaired" the TrueNAS default installation.
Anyway, the next step is to get rid of the USB key and install TrueNAS back on the NVMe SSD.
Cross fingers about this...but It's for another day.
Edit : RedCoat, here is the General information asked several days ago :
IPv4 interface says "0.0.0.0" ¯\_(ツ)_/¯