This is a comment on Cannot switch theme, posted by Abram4 at 09.06.2019 18:02

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I expected that specifying theme in the Admin Panel will certainly install it for all users. However, if a registered user has set a theme in his a profile before  changed theme by the administrator, then this setting does not change. I did not understand how to install theme for the guest. Cleaning caches of wiki  and browsers give unpredictable results. I myself am embarrassed to reproduce the issue. So far, I realized that it is necessary to allow one theme only and set it in Admin Panel. After that, I need clean all caches of wiki and browser. Then (may be) users and guests will see same theme.