From what I've googled, it looks like Netbook mode is dead in Plasma 5. That makes sense as there's a combination of netbooks mostly dying as people either use tablets or ultrabooks and ultrabooks have good enough screen resolution. But I have an old Acer Aspire One with a **** screen resolution. I think it's something x 800. If Netbook mode is truly gone, is there a way to remove or reduce window decorations to take advantage of all the screen real estate?

Yes, the shell dedicated to netbooks is gone, as that kind of device is not much used anymore (if someone wants to work on one can be discussed tough

the KWin behavior (no borders when windows are maximized) that Plasma netbook used, should still be available by editing kwinrc by hand:
adding
BorderlessMaximizedWindows=true

in the [Windows] section

Please notice that this key will likely be dropped at some point and replaced by a kwin script (in case you wonder that it suddenly stopped working)

luebking wrote:Please notice that this key will likely be dropped at some point and replaced by a kwin script (in case you wonder that it suddenly stopped working)

I don't know how much work it is - I'm only a casual developer of small programs, but a little checkbox or something in a menu would be nice.

You'll then be able to activate it in "kcmshell5 kwinscripts", but since it's a remote/secret feature (which actually requires additional help, eg. a window button plasmoid or so which would then toggle the setting) we will likely not expose it now to only withdraw (moved to scripts) it soon after.

I think that dropping the Netbook workspace from Plasma is a bad move. For one, netbooks might not be the current fashion, but they are still useful devices. One of the beauties of Linux is that you don't need the latest hardware top run it. It thus lets you extend the life of old machines, keeping electronic junk out of landfill and providing affordable options for those without the resources to pay for newer technology. Willfully dropping support for netbooks simply because they are passe runs counter to this ethos. Secondly, I still really like my old netbooks, of which I have two around the house. My Eee PC still gives me 4 hours battery life, weighs little, doesn't attract thieves, and I expect to by using it for at least another couple of years, even if I have do regrettably have to abandon KDE...