It is difficult to find resources on Seeltersk but I started a thread anyway.
Wordlist Seeltersk - German
Wordlist German - Seeltersk
Wordlist Seeltersk - West Frisian
Wordlist West Frisian - Seeltersk
Grammar (in German)
Some short texts
Local council homepage (Seeltersk / German)
https://youtu.be/AFNlZecza_k
A woman translating children's books into Seeltersk.
https://youtu.be/AuO1hFd9HDY