28.04.2020, 16:01
Finally success! Installation of the lib32stdc++6 made the trick.
I can confirm that Vapoursynth including the plugins (except the waifu2x-w2xc) compiles well on Ubuntu 20.04. I had just to change libopenjp2-?-dev into libopenjp2-7-dev in build-vapoursynth.sh and to install python3-testresources and meson packages before running the build-plugins.sh.
And I can confirm, that Hybrid starts well on Ubuntu 20.04 after installing the lib32stdc++6 package too. Sorry for my overlooking your hint on that in the other thread.
All the mentioned above has been proved in virtual Ubuntu 20.04. Hopefully it will remain true after upgrading my physical machine to it.
Thank you Selur for all your support!
I can confirm that Vapoursynth including the plugins (except the waifu2x-w2xc) compiles well on Ubuntu 20.04. I had just to change libopenjp2-?-dev into libopenjp2-7-dev in build-vapoursynth.sh and to install python3-testresources and meson packages before running the build-plugins.sh.
And I can confirm, that Hybrid starts well on Ubuntu 20.04 after installing the lib32stdc++6 package too. Sorry for my overlooking your hint on that in the other thread.
All the mentioned above has been proved in virtual Ubuntu 20.04. Hopefully it will remain true after upgrading my physical machine to it.

Thank you Selur for all your support!