Yes, but not for a specific feed. It’s all or none. You could make individual url files for each feed and call them in sequence with cron or something, but that’d probably get unwieldly. You can also (I think…) control the format of the notification.

Not sure, but here is an old reddit post about it:

https://redlib.catsarch.com/r/linux4noobs/comments/ls6mlx/how_to_make_newsboat_use_the_system_notification/

And the bash script that might work if used in conjunction with a cron job:

https://github.com/LukeSmithxyz/voidrice/blob/master/.local/bin/statusbar/sb-news