I can't use snap packages, even if installed
Solution 1:
[SOLUTION to QUESTION1]
There is some kind of bug in I-do-not-know-where.
To temporally solve this, I had to copy programname.desktop from /snap/programname/current/programname.desktop to /usr/share/applications (with sudo) and then all was fixed: programname shows in the gnome menus.
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[SOLUTION to QUESTION2]
The snap binary and desktop directories will not automatically be added to your environment variables. In order to solve this, I added the following line to /etc/zsh/zprofile:
emulate sh -c 'source /etc/profile'
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