Edit Advanced emulator configuration and change the default emulator from Mame 2003 Plus to Mame

This is the only thing that needs to be done to work.
Do you have the possibility to install the System on a USB stick and test with the system completely clean, adding just some MAME ROMS for testing, along with the BIOS needed for MAME?

Another point that is not usually considered:
You have a ROM package, but you have updated your gamelist yourself, or are you using a gamelist that came with it (imagine that there is a possibility to set the core by ROM if this is configured in the gamelist, even if you set the core to the emulator, the specific ROM configuration is what is considered).

Update your gamelist, preferably with an external software such as Skraper or ARRM:

Skraper: https://www.youtube.com/watch?v=G388Gc6kkRs&list=PL2oNQ0AT7fx2ExiSNrfHUzga5GnogI4sh&index=22&ab_channel=Recalbox ARRM: https://forum.recalbox.com/topic/11850/arrm-another-recalbox-roms-manager