If Earth was as big as Jupiter, would there still be an undiscovered continents?

If earth were as big as Jupiter, sure, there would probably be plenty of undiscovered continents or regions. High jovian gravity would likely mean any life would be low to the ground and more likely sessile than motile--unless of course it were wind blown lol, or moved around in the thick slush below the atmosphere. Even if intelligence somehow evolved, traveling and exploring, yet alone lifting (or controlling) satellites would be problematic. Even if wind borne travel were possible, visibility (even above the slush) is likely to be so poor they couldn't see anything anyway

Do you mean: 'if a rocky planet with a metallic core like earth was the size of Jupiter..."?

I doubt such a planet could exist. The heat caused by the gravitational compression of such a mass would be enough to melt it totally, and probably result in it blowing to bits.

Remember that Jupiter is the size it is; because it is mostly a very thick atmosphere surrounding a rocky or metallic core. The core is several times the mass of the earth; but very hot (about 25,000 deg C). If it was ALL rocky, its temperature would be very much higher.

I disagree with the answer saying we would be crushed by the gravity. Yes, we would if we just landed there now and wandered around but if we evolved on the planet (hypothetically) we would have somehow developed mechanisms to withstand the extreme gravity.

I would say no - we would have discovered all the continents by now due to satellites and what have you. However, before the advent of space exploration I would say there would be a possibility of continents/subcontinents being undiscovered.

No, there would be no continents, no oceans, just a massive atmosphere that would gradually change from gaseous to liquid to solid. There would be no solid surface boundary. It would be like Jupiter.

with the technology of today:

no

with the current population Jupiter could have uninhabited continents.(all hypothetical)

no because satellites would be able to map the whole planet, even at that size

No, because we would have been crushed by the extreme gravity.