Wanted to post an FYI to anyone sailing to Greenland. At least for the time being, it is such a new destination port that it seems the cruise lines still do not have excursions available for booking directly through them. You will need to do a good bit of research and find some options that work for you. Here are some things to keep in mind about Greenland in general, based on what I've learned so far:
It seems there are only a couple of port stops used at present, and they are almost always tenders
The most popular port appears to be Qaqortoq, but I've seen excursions departing from other southern Greenland locations like Ilulissat and Narsarsuaq, which might indicate other towns are being used as ports of call and not just for land vacations
Your actual excursions options are going to be somewhat limited
The most popular excursions in southern Greenland are a helicopter flight to the central glacier, and a boat ride up to a twin glacier where you can actually get off the boat and walk right up to the glacier's face (as it has receded so much over the years that it's now a short walk on land to get to it)
There are also options for things like "kaffemik" (coffee and light snacks), or a meal featuring traditional home-prepared food like reindeer, seal, etc with a local family, or other such direct interactions with the locals; these often carry disclaimers that not everyone speaks English or other European languages, so communication could be tricky if you're hoping to have a dialog and learn directly about Greenlandic traditions and customs
All such outings are expensive, costing around $35-50 USD per person for the kaffemik experience and other "time with a local" experiences, to $200+ per person for the helicopter rides; consider it to be like Alaska in that regard
The other big thing I've learned about Greenland is that there are literally no roads or other infrastructure between towns; everyone gets from one town to another by boat or helicopter. So whatever town you dock at, that is where you will be if you don't pay for one of these excursions to the more remote parts of the island. If you don't have the budget to pay for one of the remote access excursions, consider just wandering around the town and checking out what there is to see there.
Oh, and the final part that you will want to be aware of -- from June through early August is fly and mosquito season. I've seen YouTube videos where a couple visiting Qaqortoq in early July were being swarmed by flies and the guy who was being recorded had a full face covering in place to keep them out of his mouth and nose. If your trip will be visiting at this time, plan to dress accordingly and to bring bug repellent!
Here are some links to sites I found that offer excursions in Greenland:
https://arctic-adventure.dk/destination/greenland/
http://www.sagalands.com/our-destinations/
https://www.sermeqhelicopters.gl/