In normal use, the ISO is present as a block device on the hardware. All that can be hard to understand when most computering seems like magic. But in short, the ISO maker has to tailor ther installer for use with Ventoy in a generic fashion, which is an amout of extra work for them.

It is also possible for a multi-ISO boot loader to keep ISOs as block devices. But that would require different hands-on for preparing it, and the multi-ISO boot loader developer would probably need to offer a special utility for that, since it does involve slightly more than copying a file into a filesystem.

Anyhow, clearly any multi-ISO program is good for those cases where it works.

I use Ventoy because it's more handy for carrying a bunch of distros and other OSes (like the BSDs) on a single USB flash drive than dedicating one (especially an optical disc such as a CD-R or a DVD-R) to a single ISO -- and it might still not work on your hardware, so you're screwed if what you used to burn it onto is not rewritable. The only actual argument I've seen AGAINST using Ventoy is the concerns over the blobs, which you can read about here for further clarification. Even still, it's not as bad as the fact that the CPU you're using likely has a proprietary backdoor that you can't do a single thing about...

Using refracta2usb instead of ventoy.

This is how I always do a netinstall.

Next, if you come to a similar wifi issue, then use "go back" until you get the menu of tasks (which you also can get directly by choosing the "expert install" option). Then move forward using that. Feel free to come back for specific advice.

good luck.

edit: if you have a dvd-r(w) laying around, yoiuu could master the iso onto it; that works best in my experience, specially with excalbiure. (am repeating myself)