SUMMARY
When logged out or rebooted from wayland plasma the scaling (200%) global scaling is remembered and works fine. When however I log out from wayland into sddm , login into X11 and then log out of X11 plasma and log in into wayland plasma I can see small letters again. When I look in "display settings" it shows properly 200%, but it is not acted on as  all letters in plasma (K) menu are small. 
As a workaround I need to adjust slightly to 175% , press apply button and then go back to 200% and press apply.

STEPS TO REPRODUCE
1. 
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3. 

OBSERVED RESULT
Small letters in menu. Scaling not applied although it shows 200% in display settings.

EXPECTED RESULT
Proper scaling in effect.

SOFTWARE/OS VERSIONS

Linux/KDE Plasma: kubuntu 21.04
KDE Plasma Version: 5.21.4
marian@HPSpectre:~$ dpkg -l | grep plasma | grep Runtime
ii  libkf5plasma5:amd64                           5.80.0-0ubuntu1                                                      amd64        Plasma Runtime components
ii  libkf5plasmaquick5:amd64                      5.80.0-0ubuntu1                                                      amd64        Plasma Runtime components
ii  plasma-framework                              5.80.0-0ubuntu1                                                      amd64        Plasma Runtime components

KDE Frameworks Version: 5.80
Qt Version: 
marian@HPSpectre:~$ dpkg -l | grep qt5core
ii  libqt5core5a:amd64                            5.15.2+dfsg-5                                                        amd64        Qt 5 core module

ADDITIONAL INFORMATION
See attached files