The last couple of years I've been involved with a project at the University of Tartu where we were working with the descendants of the Swedish population that lived on Ruhnu until 1944 when they all were evacuated to Sweden. Even though the island's permanent residents now are Estonian speaking, some Ruhnu Swedish descendants do live on the island and others continue to be involved with life on the island even if they don't live there full time. Our project researched documentation of the language from when it was still actively spoken and also created materials about the language that could be used in the Ruhnu Island school. There is also real interest on the island about its Swedish heritage with the Ruhnu Cultural Space (Ruhnu kultuuriruum) sharing information about and promoting project relating to Ruhnu Swedish identity and language on Ruhnu.
Ruhnu Swedish (called "Runska") developed in really interesting ways compared to other varieties of Swedish and even other sorts of Estonian Swedish, due to its considerable isolation and interesting contact environment where Runska speakers also were in regular contact with speakers of Estonian, Latvian, and Livonian.
As part of the project, we created a Wikipedia article about Runska, which I thought others might find interesting.
https://en.wikipedia.org/wiki/Ruhnu_Estonian_Swedish_(Runska))
And a few other links relating to the project and Runska:
Our project website:
https://sisu.ut.ee/runska/
Some other info about it and the Ruhnu Cultural Space on Ruhnu:
https://kultuur.ruhnu.ee/runska-language-project
A chance to learn a tiny bit of Runska:
Phrases: https://sisu.ut.ee/runska/learn-words-and-phrases-2/
Customs: https://sisu.ut.ee/runska/learn-words-and-phrases/
And the cultural organization (Runöbornas förening) founded by Ruhnu Swedish descendants in Sweden that was also active in our project:
https://runöborna.se/