Did you "install" the Netinstall offline. That will install very little.
I think you should use another DVD and download an Unofficial non-free image including firmware from https://cdimage.debian.org/images/unofficial/non-free/images-including-firmware/
Try this. ip a is the same as ip addr, http://linuxconfig.org/how-to-connect-to-wifi-wlp3s0from-the-cli-on-debian-10-buster
When it comes to the second command wlan0 has largely disappeared. You need to substitute the name from the first command... So, sudo iwlist wlp3s0 scan | grep -i ssid
I know that it is usual to run servers headless - but not everyone does. I was trying to ascertain what the OP has done...
I know that many distros don't have sudo by default - but the OP is using Debian and has signed in as Root. It is enough to sign in as normal user and then use...
Why are you in tty? Did you choose to go headless? Or did you install a Desktop Environment or Windows Manager? Why do you have to sign in as Root? The netinstall would have given you the opportunity to sign in with a Username and Password. Have you tried to sign in with that? What happens? If...
You need: firmware-iwlwifi
1) How did you obtain the netinstall disk?
2) Can you connect the laptop temporarily to Ethernet?
3) Your sources list needs to be changed to include: contrib non-free
4) You can download firmware-iwlifi and put it...