[ownedbycats]

I wonder, though, what change was made so at least two antiviruses are flagging it.

VirusTotal notes that calibre.exe does write to a file inside of the Windows folder (udhisapi.dll, universal plug & play), which may be seen as a red flag. But I think older versions did this too.

Executable compression, perhaps? Antiviruses also like to complain about that as they're often used by bad actors.