kubuntu – WPS Office very slow in opening file

WPS Office is very slow in opening some files.

For example, I have this .docx file that WPS Office takes 15 seconds to open, while LibreOffice Writer opens it in 1/2 seconds.

I have installed WPS Office ver. from official website and official .deb x86_64 package.

My system is:

Operating System: Kubuntu 20.10
KDE Plasma Version: 5.19.5
KDE Frameworks Version: 5.74.0
Qt Version: 5.14.2
Kernel Version: 5.8.0-33-generic
OS Type: 64-bit
Processors: 12 × Intel® Core™ i7-8750H CPU @ 2.20GHz
Memory: 15,5 GiB of RAM
Graphics Processor: GeForce GTX 1060/PCIe/SSE2

The solution here, which implies changing the theme on which WPS Office runs, unfortunately does not work for me.

I don’t even think that the command is correct: if I run WPS Office with et -style=XXX, I can put whatever I want in XXX and it never throws any error, and I notice no difference whatsoever, nor in terms of UI nor in terms of file opening times (not even with the proposed -style=motif).

This does not answer my question as it redirects in installing WPS from snap.