Splitgate

So far I have not seen the SMG in any mode as a starting weapon but is a weapon that commonly spawns on the ground at multitudes of locations on many maps. Play your mode of choice but I recommend team deathmatch as their are often 2 spawns of it on any map. These spawns are set on a timer and if you only see a white outline at its location where it says "Submachine gun" it still has not yet spawned. But if it is spawned you can press and hold by default to swap it for your current weapon.

Now that you have an SMG you simply have to get 2500 total damage by hitting your opponents, a few things to keep in mind;

The SMG cannot ADS
It spawns with only 2 magazines (50 rounds per mag)
This weapon has very limited range, try to be close to your enemies
The SMG is fully automatic