Data shows up in correct orientation in print preview then it gets printed upside down. I’m using a brother laser printer with their drivers.
Version: 24.2.5.2 (X86_64)
Build ID: 420(Build:2)
CPU threads: 12; OS: Linux 6.10; UI render: default; VCL: kf6 (cairo+wayland)
Locale: en-US (en_US.UTF-8); UI: en-US
how about turning them in the tray ? 
I have a HLL2390DW. I used to be able to print fine with the envelope feed orientation shown on the printer. I’m not sure why it rotated 180 degrees all of a sudden.
Letters still print fine, it’s only envelopes that changed?
As you are on Linux you may get automated updates. The question would be where the origin is. LibreOffice, Cups or the “driver” for your Brother printer…