Silvally has been one of my favorite Pokémon in terms of background lore, a lab experiment able to shed its mask thanks to the kindness of the trainer who rescued it, who in turn named it based on what a great friend that was. Also the lap experiment was copying freaking Arceus in order to combat aliens from another dimension. And while Silvally may not have had the same competitive success as the Ultra Beasts, its ability to change type, enabling it to prey on the many 4 times weaknesses the UB's have means that it is somewhat successful at that mark.
Sadly Base 95 stats across the board remain merely viable, with only a few types seeing widespread play. Multiattack being buffed to massive Base 120 Power move with no downsides is not enough for Silvally remain competitive in a game where everything is growing faster, stronger, and bulkier. Silvally's wide movepool means that it can run a few different sets, but thanks to how overwhelming Multiattack his, a large portion of Silvally will be physical.
Operation: Fey Saboteur
Ability: RKS System
Item: Fair Memory
EVs: 252 HP / 4 ATK / 252 SPE
This set capitalizes on Silvally's good defenses and speed to be a menace to the opposing team, pivoting into Knock Off, Fighting and Dragon moves, crippling them with Thunder Wave and getting the heck out of dodge with Parting Shot. Leaving the paralyzed and attack dropped target perfect setup fodder for Silvally's teammates. Multiattacks laurels have been sung and even without investment can hit significantly hard. Flamethrower is great coverage, punishing Steel types that think they can wall Silvally Fairy.
Toxic/Defog - Silvally has several very good transfer only moves that can used to further sabotage the enemy team.
Other Memories -This set makes good use of the Fairy typing to excel. Other Memories that have good defensive typing can also use this set to a degree of effectiveness. Silvally Steel and Silvally Fire stand out with the large number of natural resistances they have (Silvally Fire can swap out either Multiattack or Flamethrower for Surf).