a perfectly good system shot to hell

Actually, it's running sort of okay, which is surprising, considering that I cannot find my wlan0 interface, yet I can still connect to the internet and send and receive emails; except that, as far as my system is concerned, I am not actually connected, even though I really am connected. It all started when I couldn't download packages from the repository at security.debian.org. After doing a little research, I discovered that security packages will no longer be supported for Jessie after (I think) 17 June 2018. And I had been putting off upgrading to Stretch, and furthermore I really wanted to switch to Devuan. So now I've done it, but there are a few bugs. I was worried that my system would be unusable, but instead it is just somewhat crippled. So my process was first to change repositories in my sources.list, from Jessie to Stretch, then I upgraded. Then I changed sources.list again to Devuan Ascii, and upgraded yet again. Now my network managers and other network-aware programs cannot recognize wlan0. (I use a wifi antenna to connect my desktop to the shared network in my building, which has been fairly stable.) Don't even bother suggesting that I try eth0, as there is nothing here for me to plug in *to*: it's wifi or nothing. I seem to recall that other systems (maybe Stretch?) used different names for some of the same interfaces, so it might just be a problem of renaming my wlan0 interface to something else. Only I can't find any other names. Also I cannot use Tor, or anything over proxy servers. As I said, the problem here seems to be that my system cannot find the interface that I use to connect. I can see activity over what appears to be wlan0, yet I cannot activate wlan0 either through a gui program, or by command-line, or by changing the lines in /etc/network/interfaces ... so any help here would be appreciated. It seems to be a simple basic problem, since I still have a running system with some kind of network. But yay! I have got Devuan Ascii running on my system, so I imagine the rest of my problems as just fine tuning. Please help! Bill