Drupal login error “The website encountered an unexpected error. Please try again later.” after Softaculous installation

The following problem appears after installing Drupal 9.3.7 using the Softaculous auto installation and entering into the administrator area: The website encountered an unexpected error. Please try again later.

The following error is logged in error_log file:

The problem is discussed on Drupal forums:

When the cache tables are unavailable during logging, the problem occurs (cache is generating or another query has locked the table). Try refreshing the administrator login page first, and if that doesn’t work, try one of the solutions listed above.

whoami
Stefan Pejcic
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