Goku in DBO.

In dragonball online, 20 years after DBZ, Goku and Vegeta at full power going all-out caused a supernova in their final battle. in 10 years, he was able to make his base form in GT as strong as his SJ3 form from Z. So with 20 years, How strong would his SSJ3 in DBO be? I say SSJ4 Goku, may be a bit higher.

Is DBO canon to the manga?

Haven't followed it.

Pretty sure DBO has been confirmed as canon, will look for clarification later.

This threads a little hard to answer as besides GT being non-canon to the manga, its also non-canon and contradicted by DBO.

DBO states this about a 64 and 69 year old Goku and Vegeta:
"Knowing his end is near, Goku leaves Earth with Vegeta so that the two can finally settle their score. Several years later, [astronomers?] note the explosion of a supernova. Possibly this was an aftereffect of Son Goku and Vegeta’s battle."

This is them at their strongest, so its possible their combined strength matched that of a supernova. If so it would make this Goku/Vegeta > anything from GT.

It's canon, and yeah, I believe DBO Goku>>>GT, especially if you go by GT's scaling.

Interesting.

Dbo is canon but nobody ****ing cares because nobody plays it