Glad it worked out !
NOTE: I added some code blocks around the scripts code so it's easier to see and (maybe) copy&paste for future users.

Using raspi-config to change the audio output will not write to /boot/config.txt, but will change the ALSA (sound system) settings.
Changing the settings from the raspi-config will invoke

amixer cset numid=3 2

underneath. Try running this command from the command line (exit EmulationStation via the menu or by pressing F4) and see if the settings are kept after a reboot.
If that doesn't work, then add more info about your system, as detailed in https://retropie.org.uk/forum/topic/3/read-this-first.

So apparently I'm an idiot. Following the guide over at Reddit, I missed one thing. I had the mini-hdmi cable plugged into the second port and not to the port closest to the power supply. Looks like everything is working now.

I've found a work around, if you are using a ps4 controller you could use the middle touch pad to "wake" raspberry pie. As i said, it is a work around but it is working :)

Looks like the performance is pretty poor, even without sound. What emulators are you running and what resolution are you using ?
Can you run with verbose logging enabled (switch it on in the Runcommand launch menu) and then post the log from /dev/shm/runcommand.log ?

@KN4THX Thanks to you, too. Most (all?) Linux graphical desktop environments can output their screen on multiple outputs with different resolutions. With the oldest and (still) most common X.org display server, this can be done in shell scripts by the xrandr tool*. But Retropie comes without X.org or similar display server, and I also remember reading somewhere in this forum that the Pi 3b's hardware can't output different pictures at the same time (e.g. via hdmi and composite).

* edit: I don't know if tvservice can do anything similar on the Pi.

In addition to these obstacles and unknowns, I would prefer an external solution to free the Pi from any additional cpu or gpu stress, and (with less priority) to be future-proof from significant changes in the hard- and software.

That said, if there is a software solution for cloning the output with different resolutions without slowing the Pi down significantly, I would be happy to try it. :)

@JimJames I think I have the same issue, could you remember the video or how to fix that? it would be a big help.
Thanks!

This happened to a lot of people with the new PI4 model - thinking they can re-use the miniHDMI cables they had for the Pi Zero.

Thank you,
I tried this and I found that the sound gets very choppy in FinalBurnNeo playing Street Fighter III.
Thanks anyway.

I had the same problem. The navigation sound work but with delay, i press bottom and the sound play 2 seconds later. The video screen saver is not heard. The volume control although it changes it stays at zero. But the sound in the games is good.
I have tried all the options of "Audio Card" "Audio Device", but the only one I hear something is heard with a lot of lag.
This happened to me after I had updated the Emulation Station. Before updating it worked fine.

Is there any way to fix it?

UPDATE: Thank you guys! Indeed Ubuntu was set to 4K, changed it to 1920x1080 60hz and it instantly solved the issue. Facepalm Rookie mistake! lol! I appreciate everyones help!

@daviduco AFAIk Recalbox uses version 17,not 18 available in Retropie.

@crafunzio Sorry, I dont think i have a hdmi to rf modulator. Mines a rca / av to coax. I used the pi`s 3.5 jack with a AV cable into the modulator. But you'll find hdmi to coax RF modulators on ebay / aliexpress etc for ca 10 bucks.

(But i would def recommend paying a bit extra for a pi2scart or similar if you have a european / scart crt set.)

@evilmurray said in Swap LCD controller board for LCD monitor:

SDM-S95FR

Why not just use a DVI cable. I use this all of the time for old 4:3 monitors
https://www.amazon.co.uk/AmazonBasics-Adapter-Cable-Latest-Standard-Black/dp/B014I8UL8U/ref=asc_df_B014I8UL8U/?tag=googshopuk-21&linkCode=df0&hvadid=205210909091&hvpos=&hvnetw=g&hvrand=11251004045005465518&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006828&hvtargid=pla-332486645975&psc=1&th=1&psc=1

Yes, it might be possible. You'll need to modify the autostart script in /opt/retropie/configs/all/autostart.sh and start either Emulationstation or the desktop - depending on your current TV connection.
There's a way to detect which output is connected (see this topic), so you can use something like this:

if (/usr/bin/tvservice -s | /bin/egrep 'HDMI|DVI') ; then # Start the desktop xinit else # Start Emulationstation emulationstation fi

If you have a bit of spare cash (~40EUR) get this: http://arcadeforge.net/Pi2Jamma-Pi2SCART/PI2SCART::264.html
or this http://www.rgb-pi.com/
These are dedicated RGB solutions for SCART TVs. No lag and 1:1 amazing picture quality.