because depending ln their hardware, wifi might not work out of the box, and maybe even not ethernet either

I never experienced this with tons of machines, besides Debian now comes with proprietary blobs for that kind of hardware out of the box as well.

. If it’s the iso version with the proprietary firmware already in it’s maybe…

That ISO no longer exists. It's all now on the base image.

UPDATE 10 Jun 2023: As of Debian 12 (Bookworm), firmware is included in the normal Debian installer images. Source: https://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/

"The Debian official media may include firmware that is otherwise not part of the Debian system to enable use of Debian with hardware that requires such firmware." Source: https://www.tomshardware.com/news/debian-includes-proprietary-code