since i installed debian ( ??3?? i think) , on the first xbox with a self soldered chip ( sorry, its to long ago. i use debian. startet with SuSE 4.2 but then the xbox incident with debian and so, just debian. on my server, on my vm's, on my workstation... just debian.

I'm currently on Fedora for a variety of reasons. It's relatively up to date in terms of modern technology and is frequently updated, and its a bit more stable than something like arch

I'm not really a 'starter'. I started with Ubuntu (long time ago), then used Fedora, then Arch Linux and now I settled on Debian. You can install Debian very light for example without graphical desktop or a minimal one like i3. The installation holds for a long time. No need to be scared every 6 month that a major update will break something. It does not always ship bleeding-edge software. But often that's for good.

There's a graphical installer. Setup usually goes quite smooth.

recommendation: something simple like fedora

favourite: either NixOS or gentoo

Is there actually a big difference in lightweightness between distros, that does not go back to the Desktop Environment and used Software?

Fedora Budgie spin. Budgie has been my fav on my old Lenovo T510 and my Acer Ryzen 3 laptop, to the point I'm thinking of converting all my stuff to it.

Clean and light bout 600 - 640 MB RAM at boot.

I use and really like Fedora. But the documentation for the needed multimedia packages isn't good.

Ubuntu (also as basis for other distributions) is more widely used. So you can find more instructions for that.

I were able to use my Nvidia graphics card and steam on both of them. On Fedora the Nvidia driver is in the repository. So you don't need to download from the Nvidia package. Also my fingerprint sensor on my Lenovo T15 worked out of the box with Fedora.

TL;DR: I'd say EndeavourOS.

Note that as a general rule, the more lightweight a distro is at "run-time", the heavier it is at "configure-time", because you'll have to make choices depending on your needs to get better performance. As an example, probably the lightest weight distro is Gentoo, thanks to compiler optimization and USE flags. But it's a distro with an incredibly steep learning curve. On the other side of the spectrum, there's Ubuntu, which is one of the distros that requires least user configuration, but is also a resource hog. In my opinion EndeavourOS strikes a good balance between the two factors (Disclaimer: I don't daily drive it. I've used it enough to know I can recommend it)

My answer to such questions will always be Debian Stable with the Xfce desktop. https://wiki.debian.org/Xfce

Debian is the basis on which Ubuntu (and in turn everything based on Ubuntu) is built. If you take Ubuntu, remove most of the bullshit, add a lot of well-written help documents, and do a lot of QA work and bug-fixing, you end up with Debian Stable. The only real downside is that with Debian you really need to read the installation guide. Where other distribution's installers just do things to your computer without your consent, the Debian installer will ask a lot of questions, and the installation guide gives you the necessary knowledge so you can give an informed answer. Another issue with Debian is that some default security settings are rather restrictive, and you might need the administrator ("root") password more often than you'd like (and be it only to change those settings...).

That said, there are more lightweight distributions than Debian, and more lightweight desktops than Xfce, but I think Debian with Xfce is a good compromise for a beginner, when it comes to the balance between being lightweight and still user-friendly. (I personally use Gentoo on my desktop, with the Sway window manager. That's way more lightweight, but Gentoo is a lot more complicated to set up and maintain than Debian, and Sway is, well, let's just say you need to write a configuration file in order to use it.)

Personally, I prefer Arch or OpenSUSE.

The distributions themselves are usually not the problem, but rather various programs. For example, a current browser nowadays often needs several GB of RAM.

I started with Linuxmint on my latop. It is easy to install and to use. But now I'm using Debian (stable) on my laptop. On my desktop I'm using Debian (testing) because of the newer hardware for gaming.

Ubuntu is my favourite distribution. I tried Manjaro but returned to Ubuntu because I am used to APT. I don't like pacman....

Ubuntu is very easy but is not very light. One alternative is Linux mint, fairly easy and lighter than Ubuntu.

You can Try Fedora Workstation. its good for beginners and advanced users alike. It has brought hardware support and comes with flatpak - a large repository of software.

Definitely try Ubuntu as a easy starter. Supports a lot of hardware, is a good first step.