Works for me also on Trixie. The /dev/tty handling in gpg has bitten some people since about a decade or so.
The corresponding GPG_TTY variable is documented at https://www.gnupg.org/documentation/manuals/gnupg/Invoking-GPG_002dAGENT.html and you use it yourself in your initial email. The above recommends to add GPG_TTY=$(tty) export GPG_TTY to .bashrc. If you do that, the normal cat ... | gpg --whatever should work for you, too.
