Didn't Broly already fight Ultra-Super Saiyan- Trunks, and Vegeta?
Gohan learned to become Super Saiyan in the Room of Time and Spirit.
GAL
Galan007|Quantum Observer|
👆 Trunks+Goku+Gohan+Vegeta... And I think Piccolo may have been there too(?)
And iirc, Broly also handled SSJ2 teen Gohan. Even though Gohan was weaker at that point in time then he was during the Cell saga, he (and Broly by proxy) would still be WELL above USSJ Trunks.