@mitu thanks for the help :-)
I cannot be the only one with that problem, but so far I haven't found anyone discussing these issues. might be my stupidity ... :-D
...
Dongle didn't work before, will try again now ...
I'd like to not buy another controller :-D
maybe if I install raspbian first and then add the stuff manually ...
I think I should focus on getting the controller to work and then get retropie running, since the controller is a little bit more annoying :-D
I'll reflash libreeleec some time later this week and check whether it works there, then raspbian and just add what I need to that, once the controller is working!

If I remember, I will update the post here, to at least help people in the future :-D

I just imagined it would be more complicated. thx

@cook1e_mr
Different seller, but it was these: Ebay

@mitu It will be a Spinner to control old classics like Arkanoid and Asteroid. No buttons or "press" functionality needed. Just one axis with decent response, i.e. better than a keyboard press.

The link you shared - thank you very much - looks like it could be what I am looking for. I will try later tonight and then see how I pull that new device into RetroPie/ES.

Thanks a million

@DJMoss Adding active cooling eliminated the slowdowns I encountered while running some MAME or NeoGeo games.

@mitu By saying that I use Archlinux, it was to say that I understand how it works. In the end I found the "xpad driver" bug. I could already see myself doing a new installation.

The only thing that doesn't work for me is when I run .sh to run retroarch, generate favorites ... from ssh yes. But it is a lesser evil that will have a solution.

My next system with retropie will already be a minipc with ryzen. That although I have all the consoles, I love to emulate.

@phineascage I have a similar problem. What did you do to get the controller input to work?

In the end everything is working fine ... thanks.

Thank you for confirming it for me .

@Efriim said in Installing Retropie on Raspian RPI3 B+:

Will the new OpenGL drivers ever be compatible, is it up to emulationstation devs? or will the emulators not work too? Does Pegasus-FE work with Opengl?

Most of the emulators (and Emulationstation) are using the - native - OpenGL ES stack available on RPI, which doesn't need an X.org and has direct hardware acceleration. IMHO there's little advantage in using OpenGL instead of the native stack, but I haven't run any benchmarks.
The downside of using the - new - OpenGL driver is that certain utilities that rely on the native driver (tvservice for instance) might not work and functionality that's right now included in RetroPie would not be available.
You can find the original discussion here.

@mitu It worked! Thank you!