I really don't know why Google even bought Fitbit. They had great devices, worked great as fitness tracker, but after Googles acquisition, there is really no clear strategy for the company. They now have two similar hardware products with the Fitbit smartwatches and the Pixel watch, are not integrating them into one product line and now seem to be killing Fitbit. Which they paid 2,1 billion dollars for just 2 years ago.
The Sense 2 and Versa 4 never got third party app support in the first place.
They accidentally uploaded a third party app "WellnessBuddy" to the Fitbit store once and I downloaded it on my Sense 2. Works perfectly fine. They never bothered expanding support.