You want a true mono cartridge that reacts only to horizontal movement in the groove.
Any vertical movement is ignored. There is a surprising amount of vertical movement in true Mono LPs, new or old: small warps, surface scuffs, dust/dirt in the grooves, ...
When I sell Mono LP’s, I let buyers know: playing Mono with a Mono Cartridge: surface scuffs are not that apparent, a musical experience results,
but those surface scuffs (and ...) are definitely louder/detracting when playing using a Stereo cartridge. (even using Mono MODE on your preamp does not quiet it down the same).
I have some very old mono LPs. Playing Stereo Cartridge Preamp in Mono Mode, they were like a history lesson, not enjoyable, wouldn’t play again. Now, with my Mono cartridge, they are enjoyable, I play them for me and my friends.