i can confirm that the message is something to-do with tmux - easily reproducible when I run tmux inside tilix and then run an update
As I said - I have no idea what tmux is - or how to configure it. Why it runs /etc/profile.d commands is interesting - seems excessive
Note: when I run:
ps -ef | grep gdm
I see
dad 3835 3825 0 17:29 ? 00:00:00 [gdmcheck.sh] <defunct>
dunno why that happens - certainly an area to concentrate when looking at /etc/profile.d/10-budgie-desktop.sh