I managed to get back in with this edit in wp-config:
define( ‘WP_HOME’, ‘https://lumottu.net’ );
define( ‘WP_SITEURL’, ‘https://lumottu.net’ );
After that I checked in WP Settings/General Setting that the WordPress adress and Site adress is now https://, not https://. If I go back to wp-config and erase the added defines I end up to the same error, too many redirects.