Mordenkainen’s Tome of Foes offers the option to select a different heritage for a Tiefling by replacing the default Ability Score Increase with its own (as well as by replacing the Infernal Legacy trait):
The traits of the chosen subrace replace the tiefling’s Ability Score Increase and Infernal Legacy traits given in the Player’s Handbook.
Swords Coast Adventurer’s Guide offers variant tieflings by either replacing Infernal Legacy (for Winged, Hellfire, or Devil’s Tongue) or by replacing one Ability Score Increase trait with another increasing feature (Feral):
Feral… This trait replaces the Ability Score Increase trait.
While a non-Asmodeus Tiefling subrace is not compatible with Winged, Hellfire, or Devil’s Tongue (since they both replace Infernal Legacy with their own option), a non-Asmodeus Tiefling subrace may be eligible for Feral (by replacing the subrace’s own Ability Score Increase with the Feral one). Is it?