To solve the Ubuntu WiFi issue, open the terminal( Ctrl+Alt+t) and follow these easy steps.

This problem is related to the WiFi driver on your system if hardware is working properly. Most of the time either it shows that the no WiFi adapter found or simply the WiFi stops working at all. The Ubuntu “WiFi adapter not found” problem is one of the most common issue in Ubuntu, specially in a freshly installed Ubuntu desktop. Ubuntu “no wifi adapter found”? Don’t worry, here’s the solution. I was using HP laptop and I encountered the same WiFi adapter problem after I installed Ubuntu on it. Most probably your problem is that you’re not able to see the WiFi option in the Settings and it shows “WiFi adapter not found”. In this article, you’ll learn how to install the realtek WiFi driver in Ubuntu(any version).

Tested on HP laptop, works on all laptop and Ubuntu versions having realtek semiconductor for wireless. But effectively all it would need, is someone pushing for it - to provide a (long-term-) manageable pull request with lexra support against OpenWrt/ master, kernel 4.14, musl, hostapd/ nl80211 for the wlan drivers and not too many arch specific changes (so it can be reasonably updated with the rest of OpenWrt and not stay behind).Issue solved: “No wifi adapter found Ubuntu”, Install realtek wifi driver in Ubuntu. Personally I don't think lexra will 'ever' be supported in LEDE/ OpenWrt (too different from normal mips, no upstream/ toolchain support at all, very low-end devices, the wlan situation (drivers, AP mode reliability, nl80211 support) is difficult). In terms of lexra (Realtek's reduced mips ISA) support, there is none - nor anyone actively pushing for it (as in providing patches/ pull requests against current master) chances for this to change are non-zero, but extremely low (once you'd have hypothetical lexra arch/ SOC support, there would still be the problem of the wlan drivers and current hostapd/ nl80211, to drive them reliably in AP mode).

Realtek wifi drivers