I am using Kubuntu 18.10 with a 4K monitor. Font DPI is 144 and scaling is set to 1.5 and teamviewer gui is messed up with text and buttons misaligned, etc. I had similar problems with another application that shipped its own QT libraries that didn't pick up the system setting. I suspect that teamviewer ships with old static QT libraries. The proper solution would be to use the system libraries, but that has other complications. I added the line 'export QT_SCALE_FACTOR=1.33' to the beginning of /usr/bin/teamviewer and this "fixed" the display by scaling it to 2x for the teamviewer app (1.5X1.33 ~ 2). It isn't a real solution, but an acceptable workaround. I hope this is helpful.
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