I have tried to install Debian 9 from USB on a Lenovo desktop M710s Thinkcentre (no CD drive) using the whole disk to replace Windows OS.
It breaks when having to select a mirror saying that, after pressing F4, the mirror does not support the specific software.
I thought that meant Debian 9 was not available from the mirrors (all of them) and I tried to install Debian 11 but got the exact same result.
My internet connection is through wifi Vodafone "pocketwifi" R216h which has worked for about 5 years including a number of net install. Planning to move computer to new residence in the near future, there is no point getting a fixed internet service.
It seems the causes of the problem could be many and as trivial as the Client having a different time than the Server but my problem appears to be an IP address that is too dynamic giving one IP on one computer and another next day on another machine using the same Vodafone wifi.

This wifi gadget "blew up" about a year ago but seemed to be still working after having replaced the battery which had swollen out of shape, pushing the lid off in a big bang.

I tried the install with the iso image on one USB and the non-free wifi software on another in a "firmware" directory as recommended.

Has anyone a hint of what could be the problem and how to fix it?
I do not mind replacing the Vodafone wifi modem if that would help.

Thank you for your help.

I had the same problem with a different wifi device. Debian does not support non-free firmware. Except (wink, wink) you can get a Debian 11 net installer which includes non-free firmware here:

https://cdimage.debian.org/cdimage/u...ding-firmware/

1 members found this post helpful.

Debian have decided that non free should be included in their downloads since a few weeks ago, but I think you may have to choose it somewhere in the installation process - I gave up on Debian long ago (systemd debacle) & use Devuan, so not entirely sure.

1 members found this post helpful.

Even though Debian used to not support non free firmware, the installer was able to use them for the purpose of installing the system. After the installation you were on your own.

Since you already know how it works, if you have access to another computer, use that for WiFi connection and use an Ethernet connection for the installation (assuming that there is Ethernet on that computer).

I would try though the suggestion form post #2 even though I think it will not work. The problem must be somewhere else.