By Benia on

I suffer (!) from the error:

Source database does not contain a recognizable Drupal version.

It happens when I try to upgrade a working all-fine Drupal 7 site to a fresh Drupal 8 site with the module "Migrate update" (or in its other name "Drupal Upgrade").

I've detailed everything here. Please also read the comments:

I offer answer-acceptence, thumbs up, and 150reputation bounty for a working answer.