This was announced in a Facebook post
which claims that the aircraft will operate around the 'Chanel Islands' [sic] from 'Q4 2022'.
With only seven airworthy aircraft left in the world currently to choose from, all in the Caribbean, it will be most interesting to see which airframe turns up... if it does. (Given AA's previous history of announcements which don't come to pass, it would hardly be surprising if nothing ever does.) If it did, it would be the last and only example of a type - whose manufacturing finished around 1978 (the aircraft completed afterwards were effectively kits) - flying in the UK, Europe and the northern hemisphere.
Aurigny's experience from 2013-17 suggests that it hardly will be straightforward to keep a Trislander airworthy on a sufficiently reliable basis to operate to any schedule.