Is it a commercial operation?

Hello!
SPO is not applicable (it pertains e.g. to (commercial) flights for aerial surveying or photography, but not for operations involving paying passengers).

To specifically market sightseeing flights with passengers an A-A AOC is required. I believe an AOC is required for what you plan to do.

Just for completeness:
Operations with passengers are also allowed for organisations (e.g. flying clubs or DTOs/ATOs) in order to promote recreational flying (aerial sports) - based on an EASA Air Ops derogation. These „introductory flights“ may create revenue (= be commercial without an AOC), however this activity has to remain a marginal one compared to the main scope of the organisation.

So for instance, depending on the national competent authority, a flying club or ATO with N number of flight hours per year may conduct 5% of N hours per year conducting introductory flights. (Just an example).

See here https://www.caa.co.uk/uploadedFiles/CAA/Content/Standard_Content/Genera…
or use the many other sources available.

You must bear in mind that the interpretation of "marginal" is different in different Member States. It could be 9% or indeed 5%
I would say that commercial sightseeing tours with an aircraft are subject to an AOC. Introduction flights are not intended for regular sightseeing tours I would have thought.

Another topic is the CPL light ( for para dropping, sightseeing en other simple commercial activities) was under discussion some time ago. Does anyone have an update on this topic?

Hello Martin,
for sightseeing flights with passenger, you will need an "A-A AOC" at least in Germany. It is not that complicated to get one, it depends on aircraft and the area/legs you want to fly.
To get a "A to B AOC" is quite more difficult and it will take longer to get everything (books, checklists, postholders, etc.) certified. Let me know if you have any further questions.
Stay healthy!
Michael