germany – Long term Car rental in Europe

There is a question here about Car buying vs. long term rentals as it relates to the US.

Recently I’ve driven through Europe renting a car in Frankfurt for about 21 days from Sixt and I was wondering if there was a better option to do long term rentals like this in Frankfurt or any other major hubs in Europe so I don’t need to pay for the car at a daily rate?

If it’s too broad I am perfectly happy limiting this to Germany.

P.S. I’ve checked my usual go to services like Turo and Toyota Rentals and they don’t seem to be available in Germany.