will a video shot from a samsung galaxy S8 be OK?

It was accepted! :-)

Cell phone camera are great when they are the only camera you happen to have with you at the moment you need it. Technically the sensor smaller than your little fingernail, the lens about an 1/8 of an inch. Yes it can work but the footage at 100% will fall apart. If used in a news broadcast, cell phone, tablet or even a laptop it will look nice. That is what they are made for. There are many high end producers that will not buy photos or footage unless it comes from a limited list of quality cameras. So yes keep it available, first choice ... never. Will clips from it be approved and sell. Yes, based on subject. Great quality digital cameras with 4/3 or 1 inch sensors are cheap. If this is a hobby then go for it. If you want to make real money then invest in your business. The Artists here that are making a good full time income invest in quality cameras.