For 2.6.18 (dm800) I have the following wifi drivers: rt61, rt3573, rt5572, rtl8192cu, rtl871x, rt3070, mt7601, and rt73.
But some of them may need manual modprobing, so if the wlan device doesn't show, then try to add them to /etc/modules-load.d/yourdriver.conf
Also check dmesg for some debug info.
Please note that some of the above drivers do not work with every revision of the supported wlan chipset.
Like I said the dm800 is very old and it's kernel dates back to 2006.
You probably won't find any N or AC sticks being compatible with linux 2.6.18.
If you really need wifi then go the easy way and buy some wireless to ethernet bridge device.
In other news, all of my builds failed last night due to gitlab (iptvplayer) being down again.
So I'm continueing right now.