I’ve used fields login, password, service (pppoe). Ok button is inactive. I can establish it that way using Ubuntu, but not with Manjaro. What to do ? Also interesting why is that, whose fault is it - arch or manjaro developers ?
Do you have a adsl modem for your computer that needs a specific kernel module loaded?
No, I’m connecting cable right into laptop. I tried Manjaro KDE - the same problem, but in Manjaro XFCE DSL connection works.
This might be a plasma-nm issue.
You could try using the network manager curses based graphical frontend in yakuake or konsole.
nmtuiUpdate:
I don’t have a DSL connection so I made a dummy connection to test with, here is what I found:
After entering bogus information in the DSL tab, I had to click on the wired tab, then click on “Restrict to Device” and select a listed device before the OK button would show. I could then go ahead and remove the restrict to device entry before clicking on OK.
I hope this has helped.
PS. It might not actually be a bad idea to restrict the device though, just a thought.
Thanks, works both ways.
Why would I want do do that :
I don’t know, I haven’t used DSL in years. 
I just noticed that I could remove the selection and the OK button didn’t grey back out.