Hi, I need some help:

Today I got a new "lte router" (it uses the mobile internet, which is many times faster than the conventional internet that I used before). My girlfriend's Windows PC is perfectly connected, as is my smartphone (original Iphone SE) and my tablet (an iPad).

My laptop with Slackware current also connects via Ethernet without any problems, but not via WiFi. I am using NetworkManager and when I try to connect through nmtui I get asked for a password multiple times. At the end it will say that a password is required but not given. When I try to connect through nmcli and provide the password as an argument, it times out after a while. I've already tried not to set a password at all, but then it expires after 90 seconds with no successful connection.

I've tried almost every possible combination of settings in the router, but couldn't find a solution. Here are the settings right now:

SIM card status:
SIM card ready
Connection status:
Connected
Network name:

Network type:
LTE
Profile name:
congstar Internet
IPv4 address:
10.163.165.24
IPv6 address:
2a01:598:b889:b8e3:65a3:ed5d:8105:76e6
Cell ID:
26546947
RSRQ:
-10 dB
RSRP:
-110 dBm
SINR:
-110 dB
PLMN:
26201
Network mode:
Auto
Connection mode:
Auto
Automatically connect even when in roaming:
On
Profile name:
congstar Internet (Default)

Wi-Fi 2.4GHz:
On
SSID:
congstarMoritz
Country/Region:
Germany
Security:
WPA2
Encryption:
AES
Wi-Fi password:
its a string of numbers, so this should not be the problem

Ah, I almost forgot an important detail: this is the only network where I can't connect to with my laptop, no problems with other wifi networks

There is also a table "Connected devices" in the interface of the router. When I try to connect I can see my laptop there for a moment, but without an IP address. It disappears after a few seconds ...

WPA network? What are you using to authenticate? wpasupplicant, iwd?

https://wiki.archlinux.org/index.php/NetworkManager

The default setting was WPA2, but like I said, even if I disable all authentication on the router, I still can't connect. So I don't think that's the problem

You probably could temporarily connect via Ethernet, go into Router Firmware at it's base address and with those Admin privileges setup your WiFi MAC as something like "trusted". At the very least you'd have the most pertinent information how to connect via WiFi given that Admin status. Sorry I can't be more specific but I don't know your exact router and I haven't used WiFi in years.

Yes, connecting to the router via ethernet is possible, with firmware you mean the settings page that can be viewed with the browser after one has connected to the router, right?

There is a MAC filter option in these router settings. The default is no. Other options were blacklist and whitelist. I tried the whitelist and added the MAC of my laptop's wlan0. This did not solve my problem...

Was that what you mean or are we talking about something else?
Sorry I don't know much about networks.

Hello M0M0,
You understood correctly and did execute the first step properly as far as I can tell, namely whitelisting your wifi mac. Different firmware behaves differently of course so whitelisting may never be enough by itself on your firmware. It's just a useful step that could have possibly solved your problem, but it never was a certainty due to such differences. It is probably a good idea to leave it whitelisted for future efforts though.

If you have any doubts about the security protocol or the correct passphrase, you can reset them in that firmware. To be absolutely certain we are talking about the same thing, the firmware app is located at the Gateway address, commonly something like 192.168.0 or 10.0.0.0. Upon executing that address in your browser you should be greeted by a login prompt, usually with Admin or Administrator as "User" and the "Password" originally shipped with and noted on the label of the router. The "Password" for logging in directly to the router is different from the passcode phrase for wifi, but can be reassigned within that firmware app. That, at least, should reduce or destroy any disquieting worries that you may have entered anything (SSID or Passphrase) incorrectly from NetworkManager, WICD, /rc.d/rc.inet1.conf or whatever you are using to manage wifi and try to connect.

Again I must apologize for being at all indirect or hesitant but as I said I don't use wifi anymore. I do seem to recall that the last time I used wifi there was more than one setup, one for a default lower speed connection and another for a faster connection. It'd be good to see if your router has such options and also to label them in a way that will be obvious to you so you don't mistakenly use a slower speed connection or one that doesn't use the protocol and passphrase you know or did assign. Obviously that could be why it hangs after entering your passphrase - wrong connection.

BTW some firmware has good documentation to help you in proper setup. It might be valuable to try to find a "help" tab or follow a setup guide. It also might help to visit the manufacturers website to see what help they offer.

Best wishes...

This might be worth a try:

Open /etc/NetworkManager/conf.d/00-dhcp-client.conf as root and comment this line
while uncommenting this line:
There have been a few (less than three over many years) networks to which dhcpcd simply would not connect, and the symptoms were similar to what you're seeing.
You will have to restart NM after making that change.

That sounded promissing. Sadly there was no success either, still the same problem

How many devices are on the 2.4GHz spectrum? A new router and a fairly recent laptop should have dual-band wifi, with 5GHz preferred in a congested environment.

Ok then we talked about the same thing. I made sure the correct SSID and password are being used (or no password if I disable authentication) and it works with any gadget other than my Linux laptop. I haven't seen two different speeds, there is only 2.4 GHz or "off".

They asked me if I wanted a newer router with 5 GHz which was quite expensive or an older one that only supported 2.4 GHz. I decided to take the older model since it was way cheaper.

What do you mean with how many devices? Via wifi two devices are connected to the router at the moment and the laptop via ethernet.
Or do you mean how many other networks are around? I can see seven in the NetworkManager interface

It's unlikely to be the cause of your problem but in Europe there are only 13 channels on the 2.4GHz band. Given that you need "space" between channels, just as you need space between 92FM and 93FM on your radio to avoid stations interfering with each other, realistically you can only have six or seven devices on the 2.4GHz band to avoid devices contending with each other. You have seven routers broadcasting in your vicinity at the moment, meaning you are already at the limit, and that's not counting microwave ovens, cordless phones, and other devices which also compete for the 2.4GHz spectrum.

As I say, it's unlikely to be your problem, but I think even when you finally get it working you may end up with network dropouts and collisions.

If it turns out this way, one way to solve it would be to get a dual-band wifi access point (2.4 and 5GHz), connect it to your router by ethernet and use the wifi on your access point instead, turning off the wifi on your router. TPlink is usually reasonably priced.

You could also try a cheap TPlink USB wifi adapter, which might bypass any problems your laptop adapter has with that particular router.

Sorry I can't help with your problem any more than that.

That indicates to me that the problem is not from the router since other devices connect via wifi and you eliminated the security protocol mismatch possibility (only temporarily I hope ). So we need to focus on what is missing or blocking within the laptop config. What output do you get from "iwconfig"?

BTW do you think 2.4Ghz will be as fast as your wired connection?

That makes sence, indeed network dropouts are there. But as you said, I don't think thats the main problem since other devices connect without problem.