Is there an Ubuntu Server version with GUI available to download? [duplicate]

There is no Ubuntu Server ISO with a gui.

Ubuntu has many ISOs which contain desktops; they're called Ubuntu Desktop or flavors of Ubuntu each with the default desktop (apps & sometimes toolkits/libs) replaced with other choices.

Servers are usually serving other machines, where a GUI will just waste resources thus reducing efficiency. As efficiency is a goal, GUI is not included.

Many Ubuntu ISOs are available, the difference being the default packages included; so grab the closest to your need & add the packages required (ie. apt install, snap install etc though if you want a package manager (eg. aptitude) to automate some of this choices are always available).

No special tool is required; as standard package commands are all that's needed to add a desktop.

You can look at the manifest etc (available where you download an ISO) to see the packages included; it's an easy way to compare with other ISOs as there are many ISO choices available, should you want to find an ISO that contains most of what you need... eg. https://cdimage.ubuntu.com/ubuntu/releases/21.10/release/ubuntu-21.10-live-server-arm64.manifest (also note some install options may result in different packages actually installed)

No, not included in the iso. However, you can install using the server iso and then use tasksel to install the desktop.

First, install the server from the iso.

Next, boot up and run the following commands:

sudo apt update
sudo tasksel

If you get a "command not found" error, run the following commands:

sudo apt install tasksel
sudo tasksel

Then, select the ubuntu desktop from the list. DO NOT select any of the "live" versions.

Use the arrow keys to navigate, the SPACEBAR to select, and the tab key and ENTER to select OK when you are done.

NOTE: because of a bug in tasksel, DO NOT use tasksel to uninstall packages. ONLY use tasksel to install.

Reboot after installation and you will have a working desktop.