Because Raspbian doesn't like omxplayer, they took it out of its repos, but it is still required by emulationstation and kodi and others.
Raspbian says to use VLC, but the documentation or the fixes to start using VLC aren't visible right now.
Here's how to go backwards and get a compatable version of omxplayer installed as of 2024Q1.
sudo apt-get install gdebi-core
mkdir -p $HOME/RetroPie/omxplayer_install_package
wget --no-check-certificate -w 4 -O $HOME/RetroPie/omxplayer_install_package/omxplayer_20180905+git061425a-1_armhf.deb https://archive.raspberrypi.org/debian/pool/main/o/omxplayer/omxplayer_20180905+git061425a-1_armhf.deb
sudo gdebi $HOME/RetroPie/omxplayer_install_package/omxplayer_20180905+git061425a-1_armhf.deb
I did the above... it didn't quite work. It failed with:
Dependency is not satisfiable: libavcodec57 (>= 7:3.2.10)|libavcodec-extra57 (>= 7.:3.2.10)
I installed the available libavcodec packages
apt search libavcodec
sudo apt install libavcodec58 libavcodec-extras
It still didn't work... so then I found a newer package to download and install in the thread referenced below.
Originally from: https://forums.raspberrypi.com/viewtopic.php?p=1936216
Wed Dec 22, 2021 12:27 pm Hello, I use omxplayer just like you. I start without x and then play a mediafile via the omxplayer and now ive found a way to get the omxplayer to play.
you need first
sudo aptitude install libavcodec58 libavutil56 libswresample3 libavformat58
sudo dpkg --install omxplayer_20190723+gitf543a0d-1+bullseye_armhf.deb
from here http://archive.raspberrypi.org/debian/pool/main/o/omxplayer/omxplayer_20190723+gitf543a0d-1+bullseye_armhf.deb and after then also need rpi-update
sudo rpi-update
After the update you will not see any output on your screen but you will still be able to connect via ssh. You need also comment out this in /boot/config.txt
#dtoverlay=vc4-kms-v3d
After all omxplayer runs again.