Perhaps only mildly interesting but I just did an apt show for birdtray on Debian 13 and got this in the second paragraph of the description:

It is a nasty hack – an external process looking at Thunderbird’s insides, it suffers from problems like noticing new mails only after a delay, having to restart Thunderbird just to hide its window, etc – you’d want to use an extension like firetray instead – but, it is likely that support for Thunderbird XUL extensions will be dropped soon, possibly by the time you read these words.

Not used to seeing this kind of language in the Debian repos tbh.