Wanted: Check out solution that supports both setup and subscription fees.

Something that is either hosted or easy to install. (free and open source).

Should support SEPA Direct Debit. Preferably with Stripe support.

witness - organiser - dad - kitesurf - NL - developer
Working on Sparkly

With Stripe Billing, you can configure both a one-time fee and a subscription fee based on units of usage (which, in your case, would be amount of days). Also supports SEPA:…
Requires more programming than Stripe Checkout, though. But with the documentation and examples, you should manage to get it working relatively quickly.

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