The reference period is probably most strongly influenced by the degree of grinding and the quantity of powder. As I said, I don't miss this attitude with e.g. Solo and Passione.
However, I still doubt whether the "bitter" coffee of the TE is caused by over-extraction, or rather over-dosing in connection with flat preparation and not optimal coffee (for the taste of the TE). Therefore
my recommendations go rather in the direction of somewhat higher-quality beans and smaller powder quantity, but perhaps via "aroma" to deepen the reference time a little? I would
not put too much around
at the grinder - in
my experience they are factory-set quite reasonably and should only be readjusted after longer use.
Crema or espresso blends can only be judged at the manufacturer, I personally usually end up at the KVA with intensively roasted espresso blends of medium quality (up to 20€/kg) and high Robusta content.