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Hi Stefan,

I treid another way:

First downloaded only the package from your source.

2025-04-15 13:52:39 URL:https://linux.brostrend.com/rtl8821cu-dkms.deb [4035666/4035666] -> "rtl8821cu-dkms.deb" [1]

Then just installed it using

dpkg -i rtl8821cu-dkms.deb

This built automatically the kernel module and installed it:

--- snip ----

LANG=C dpkg -i /home/ullhan63/Downloads/rtl8821cu-dkms.deb
(Reading database ... 574778 files and directories currently installed.) Preparing to unpack .../Downloads/rtl8821cu-dkms.deb ...
Module rtl8821cu-5.12.0 for kernel 6.1.0-33-amd64 (x86_64).
Before uninstall, this module version was ACTIVE on this kernel.

8821cu.ko:
- Uninstallation
- Deleting from: /lib/modules/6.1.0-33-amd64/updates/dkms/
- Original module
- No original module was found for this module on this kernel.
- Use the dkms install command to reinstall any previous module version. depmod...
Deleting module rtl8821cu-5.12.0 completely from the DKMS tree.
Unpacking rtl8821cu-dkms (5.12.0-16b11) over (5.12.0-16b11) ...
Setting up rtl8821cu-dkms (5.12.0-16b11) ...
Loading new rtl8821cu-5.12.0 DKMS files...
Building for 6.1.0-33-amd64
Building initial module for 6.1.0-33-amd64
Done.

8821cu.ko:
Running module version sanity check.
- Original module
- No original module exists within this kernel
-

On Tue, 15 Apr 2025 13:58:51 +0200
Stefan Schumacher <[email protected]> wrote:

Hello
I recently bought a BrosTrend 650Mbps Linux Compatible Wiki Adapter (https://www.brostrend.com/products/ac5l) lsusb shows it to be a:
0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC
They seemed rather linux- and especially Debian-friendly and even have
a web page just for Linux: https://linux.brostrend.com/

Clicking their link causes the installation of a kernel module via
DKMS.

Did you attempt to use the kernel module supplied with your kernel?
Searching on the device ID you gave indicates that the device has been supported since kernel 6.2 and on Debian 11. https://linux-hardware.org/?id=usb:0bda-c811 You may need a backported
kernel.

--
Does anybody read signatures any more?

https://charlescurley.com
https://charlescurley.com/blog/

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Stefan Schumacher wrote:

Hello
I recently bought a BrosTrend 650Mbps Linux Compatible Wiki Adapter (https://www.brostrend.com/products/ac5l) lsusb shows it to be a:
0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC
They seemed rather linux- and especially Debian-friendly and even have
a web page just for Linux: https://linux.brostrend.com/

Clicking their link causes the installation of a kernel module via
DKMS. Unfortunately it stops on my current Debian 12 with the error
message copied at the end of the message. I bought this at Mindfactory
and the support told me that they only give support to people who
either bought directly from them or via Amazon. Doh.
Does anybody have any suggestions on how I can get this device
working? I mean it's Realtek, I remember using Realtek-8029 cards
because they were a) cheap and b) worked always without problems.

...

- Original module

- No original module exists within this kernel

- Installation

- Installing to /lib/modules/6.1.0-32-amd64/updates/dkms/

depmod...

modprobe: ERROR: could not insert '8821cu': Key was rejected by service

Aborting, command failed: modprobe 8821cu

This is a secure-boot message; the kernel isn't allowed to load
this module because it isn't signed by the upstream key.

You can turn off secure-boot, if that's an option for you.

-dsr-

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