I am not sure I understand you correctly, but when you ask if it is possible to have an automatic login in the GUI as one particular user direct after boot, the answer is Yes.
YaST > Security and Users > Users and Groups.
Then there is lower right: Advanced Options. This opens a new window where the first item is: Automatic Logon and then you can schoose the user that is loged on automatic.
BTW, personaly I see this feature as a thread to securiry, but YMMV.
I am seeing some certificate errors and an IOMMU error (on your screen image).
No, I do not see those here. The IOMMU error could be specific to your hardware – or maybe not.
For the certificate errors, I assume that you have secure-boot enabled. Those probably go away if you disable secure-boot. You might want to experiment with that just as a test.
When first booting, you probably saw a blue screen to approve using the openSUSE certificate. And you probably agreed to that – I don’t think you can boot with secure-boot if you don’t agree.
Then, probably after the first kernel update, there was another blue screen. If you took the MOK management option, you would have been asked to install another key. If you instead went with “continue”, you would not have installed that key. My guess (and it is only a guess), is that you went with “continue” and those certificate errors are because of that choice.
And, by the way, I do think those blue screens are confusing.
On the initial boot screen, it will boot without further action after a timeout. You can set the timeout to 0 to skip that, though I would suggest instead to set it to 1 second. You can make that change with Yast Boot Loader.
Maybe you should explain better what you mean with expressions like “joining”. That might sound as a nice word, but it means nothing in the area we are talking about here.
When the system boots, there is first the Grub screen where you can choose what you want to boot (in a multi boot configuration) and it gives you the opportunity to deviate from normal booting in the case of problems (you can then use an older kernel) or tests (adding kernel parameters), etc. It waits by default 8 secs and then starts the default boot entry. As @rnickert explains you can cut that down, but be sure you still might need that opportunity to intervent some time in the future.
Then the real Linux/openSUSE boot starts. It might show some image, or just the lines of what happens (you can switch from the image to the lines using Esc).
And then shows the Graphical login screen. Boot is now finished, the system is fully up and running, including eventual service deamons. A user can then log in. As I explained earlier, the system manager can arange it for one of the users to be loged in automaticaly.
Oh yes, and please do not compaire with what Windows does. I wouldn’t know and Linux is not Windows.