All of the AM4 motherboards are supposed to be compatible. Each of the A320 / B350 / X370 chipset motherboards requires a UEFI update before it will work with the Ryzen 5 2400G. Motherboards that have been stocked in the past couple of months already have compatible UEFI - many of these have a sticker on the box to indicate this - but old stock motherboards may have older UEFI that are not compatible. Some of those boards have a UEFI "flashback" feature that allows UEFI to update without a compatible processor (some of the Gigabyte boards have this). Motherboards with older UEFI and without flashback feature will need to first be updated with a first generation Ryzen processor.
If, "What GPU's can work with this processor" means which will work with dual graphics, then dual graphics is not supported for the Ryzen APUs. Go with the integrated graphics until you can afford a discrete graphics card.