Here are some combos I found at Shadowloo Showdown UK:
Anywhere:
Jump HK, cr HP xx LK Duck -> Skyscraper (launch), Ducking Body Ducking Hook, cr.MK xx Sonic Fang. 394 Damage.
Ducking Body Ducking Hook, cr.LP x cr.MP x cr.HP (3 hit chain) xx EX Sonic Fang (launch), cr.HP xx LK Duck ->Skyscraper, Ducking Body Right Hook, HP Flicker. 350 Damage.
Ducking Body Ducking Hook, cr.MP, cr.MP xx Hellfire. 226 Damage.
Ducking Body Ducking Hook, cr.MP, cr.MP xx EX Hellfire, Hellfire Rush. (3 Bars, EX move link to Super). 436 Damage.
Cr.MP, cr.MP xx LK Duck ->Fox Hunt xx EX Sonic Fang (launch), cr.HP xx LK Duck -> Skyscraper, Ducking Body Ducking Hook, Flicker (any button depending on how you want to end it). 450 Damage.
Corner Combo:
EX Flicker, LK Flicker, Cr.HP xx Hellfire. 364 Damage.
Cr.HP xx LK Duck -> Skyscraper (launch), Weaving B, Shoulder Rush, Uppercut (Relaunch), cr.HP xx Hellfire Rush. 509 Damage.
Notes:
Ducking Body Ducking Hook is his charging punch, performed with Towards + MP, LP. Interestingly, it’s bufferable, so if you do Towards + MP, and then press LP quickly afterwards (but not too quickly), then Steve will go into the second part automatically, even if the first part of the move has not connected yet. That gives you enough time to connect with a follow-up if you hit. Cr.LP is the easiest, Cr.Mp is a little trickier but do-able and cr.HP is possible but really hard (I guess a 1-framer, I did it by plinking). If the move is blocked, then I just went into cr.MP x 2 xx LP Hellfire for pressure.
Skyscraper is the optimal launcher to start a combo, but only cr.HP puts the opponent into enough hitstun to land it. Or you can use an EX Duck and land it, so you could also do cr.MP xx EX Duck -> Skyscraper.
Launchers:
Steve seems to be very Tekken-esque (unsurprisingly) in that he has a number of launchers. some being better than others. Here are the launchers I found so far:
Skyscraper.
EX Sonic Fang.
Weaving B, Shoulder Rush, Uppercut chain. (Loads of time to juggle, but really hard to land, outside of the corner).
EX Flicker.
I’m pretty sure he has others, like one of the follow-ups from Peekabo, and I think the EX Sway might also juggle.
Massive thanks to XShoryuken 26 for the damage numbers.