True, 1.6 no problem at all. A fresh installation with 1.7 also no problem. Only a migration from server with Prestashop 1.7 causes problems.
What I determine. With a fresh installation of prestashop 1.7 (on a server with msqlnd) ,these drivers are automatically installed and the datebase is linked without errors.
This must be done manually during a migration ( server with musqli 5.x). PHP files must be modified to load appropriate drivers.
But ... I have no idea where or how to do this.