Version 4.2 Tin Whistle plugin tested on MuseScore 4 v4.2.1
Plugin file: tin_whistle_tablature.qml
Whistle instrument file: all-whistles-v4.xml
Note that this is may not be compatible with earlier versions of MuseScore 3 and MuseScore 2 - use the previous releases for those.
A font file TinWhistleTab.ttf is attached for convenience from Blayne Chastain and states:
Tin Whistle Tab font is free of charge for both personal and commercial use. Distribution for a fee is not allowed. Please credit Blayne Chastain in any publication in which this font appears with the following copyright notice: "Tin Whistle Tab font © Blayne Chastain / www.blaynechastain.com"