Seems unlikely that Starlink would put a base station on Saint Helena just to be able to serve some percentage of ~4000 population. Most likely the base station is somewhere else.
[0] https://www.sainthelena.gov.sh/2023/news/lease-signed-with-o...
[1] https://www.sainthelena.gov.sh/2020/news/satellite-ground-st...
Base stations on remote islands are a routine thing to construct. The British Empire built the first global telegraph network using their island colonies, and some of these routes are still used for Internet cables. Ascension Island for example.
https://www.starlink.com/maritime
https://support.starlink.com/?topic=9eb841b3-2e43-a6fb-ecc7-...