Hm, this should not be the case.
Have you tried a fresh user account? Are the default widgets missing there too?
Widgets you added manually in KDE4 will be missing though, that’s “normal”. Plasma5 doesn’t use or migrate the KDE4 desktop settings (except some). As widgets have been added/removed/renamed and their configuration might have changed too, that’s not really doable in an automated fashion.
One problem I’m still having is that programs (especially Firefox) refuse to redisplay when I switch away from them. If I’m using Firefox & click the Konsole icon in the task manager then click on the Firefox one, Firefox won’t display.
Hm. I never saw that either.
Does switching with Alt+TAB work as expected?
There might be a problem with refreshing the graphics, so try to disable desktop effects and see if that helps.
There is one other problem that I’ve been having, the entire system becomes unresponsive at least once per day and if I’m listening to something (using VLC) the last 2 seconds of audio repeats infinitely. I’d suspect a video driver problem except I’d get the exact same symptoms on my very old SUSe 11.2 system that had the NVidia driver (but only every 2nd week or so).
Well, there could be other reasons for this as well (like the system overheating, bad hardware, …), but graphics driver problems are indeed a likely candidate.
Nouveau still has problems, depending on your exact graphics card model.
You might try to install the proprietary nvidia driver and see whether this helps, but that can be a hassle on Tumbleweed.
And at the moment, only the latest 346.xx (G04) version supports kernel 4.0, for the legacy drivers you need an additional patch.
But if your graphics card is “only” 2 years old, the latest driver version should support it I think.
Again, booting to recovery mode (or adding “nomodeset” to the kernel boot options) would be a (probably) quick way to test whether your problems are related to the graphics driver, but especially “recovery mode” might workaround other hardware/driver problems as well.
At least systemd does sometimes log an error in these cases. Can I send the logs somewhere?
http://susepaste.org/ maybe, or upload the file(s) to any other file sharing site and post a link.