All stars and planets retain their size and shape due to the balance between gravity, which tends to compress them, and pressure, which, on the contrary, tries to break them. If gravity disappears, then the balance between these two forces will be disrupted and the huge internal pressure will lead to the explosion of all stars and planets, only dwarf planets in which the pressure is not so great and does not exceed their own strength can survive in theory. Due to the disappearance of gravity, nothing will hold matter in star systems and galaxies, the debris will retain its momentum in space, as it was at the time of the disappearance of gravity and will scatter across the Universe. In a few tens of millions of years, galaxies will cease to exist as clusters of matter, and in a few billion years, superclusters will cease to exist.
When all the stars and planets explode at the same time, all life in star systems will stop, only those who will be away from the stars, on spaceships, will be able to survive, but this will not last long. With such an explosion, the universe will be illuminated by the brightest radiation in all ranges, sufficient to destroy all life in the galaxies, it’s only a matter of time before it reaches ships far from the stars.