mode11 I confirm your argues. On my part, I was writing a Linux script to auto scale and centering games on my CRT screen without any overscan into 15.7kHz (cf: https://forum.batocera.org/d/5865-scaling-all-games-properly-with-retroarch-on-a-crt-tv-screen). Now, everything works great with Batocera .30 with dynamic resolutions ingames and I was looking to update to the new .31 release to provide and share my fix.
But if I can’t play new emulated roms with libRetro Mame and use it’s fantastic run-ahead lantency functionality, I’m not sure using Batocera is still a good deal.
Edit : I had a quick look on the Batocera .32 dev release. It seems the Mame libretro core is back.
I found in the es_systems.cfg file :
<system>
<fullname>Mame</fullname>
<name>mame</name>
<manufacturer>Arcade</manufacturer>
<release>1997</release>
<hardware>arcade</hardware>
<path>/userdata/roms/mame</path>
<extension>.zip .7z</extension>
<command>python /usr/lib/python3.9/site-packages/configgen/emulatorlauncher.py %CONTROLLERSCONFIG% -system %SYSTEM% -rom %ROM%</command>
<platform>arcade</platform>
<theme>mame</theme>
<emulators>
<emulator name="libretro">
<cores>
<core>mame</core>
<core>mame0139</core>
<core default="true">mame078plus</core>
</cores>
</emulator>
<emulator name="mame">
<cores>
<core>mame</core>
</cores>
</emulator>
</emulators>
</system>
And the file /usr/lib/libretro/mame_libretro.so is available again.
So I feel confident, it was just a bad dream.