So new here. I would like to thank you for your comments about Pabbly<>Digistore24. Now I understand it much better.

Regarding your questions:

Digitstore24 handles all payment matters; you conclude a contract with them yourself. You sell the courses/digital products. So you really have nothing to do with taxes, no matter where. They offer all important payment functions for the end customer. When purchasing, the customer always concludes a purchase contract with Digistore, so you are also “out of” various other legal obligations. However, all copyrights remain with me. You will then receive the total income transferred once a month. You declare this yourself as part of your income tax return, and that's it. So you have nothing to do with the other tax tasks. I think this is perfect. Of course, they get a fee for each sale, which they deduct. But I think that's okay. This saves you the tax advisor, costs for third-party software such as Quodernate or similar, you don't have the administrative effort, etc. In addition, they offer their own marketplace where the products are offered directly and an affiliate program, which you don't have to use, is optional.

You can find all features of Digitstore24 here:
https://features.digistore24.com/en

Digistore24 is therefore very popular in German-speaking countries (D, A, CH, etc.), an identical alternative is CopeCart. Digistore24 is now really a global player, although not quite like Paypal (my personal opinion).

Other LMS (e.g. https://www.mentortools.com/ or https://docs.coachy.net/en/integrations/digistore24/connect-digistore24/) integrate Digistore24 directly via API key.

This has the advantage that everything runs directly through the academy, but you can also find the products at Digistore24. But you don’t need their landing pages. In the LMS, however, the payment process is as described above. Senses and checkout used. The course's own LMS landing pages can be used, the academy remains public. Perfect in my opinion.

If you would connect it via API, that would be perfect. The same applies to Copecart. It would also be perfect for me if you offered such a service as an alternative. In other words: You sell the courses as a seller, including the payment process, take care of all taxes and pay out once a month, minus fees. But I strongly suspect that it's far too much effort for you and you won't do it, right?

Digistore24 and CopeCart have been mentioned here several times in passing, but they are very popular. Integration via API would be perfect, natively like you have integrated Paypal or Stripe. I would find it disadvantageous to make the academy private and not directly accessible, especially since marketing etc.

Thank you again for the detailed information and quick response. Feel free to comment again what your opinion is.