AMD's 300-series motherboards were never part of the chipmaker's support plan for Ryzen 5000 (Vermeer) processors. However, an avid enthusiast (via HKEPC) has modified ASRock's firmware to support AMD's latest Zen 3 chips.
First and foremost, it's important to emphasize that it's a Beta firmware, and an unofficial one at that, which doesn't come from ASRock. An unknown source provided the firmware files to Hong Kong-based news outlet HKEPC for distribution. The publication has tested the firmware and confirmed that Ryzen 5000 processors indeed work without hiccups on the select few X370 ASRock motherboards. Of course, there are bound to be bugs or stability issues with unofficial firmware, although none have been reported so far that we know of. So, use at your own risk.
The altered firmwares are vailable for six ASRock X370 motherboards, including the X370 Gaming K4, X370 Gaming X, X370 Killer SLI, X370 Killer SLI/ac, X370 Taichi and Fatal1ty X370 Professional Gaming.
Getting Ryzen 5000 processors to work on unsupported motherboards is one thing. But yu'll still be losing out on PCIe 4.0 functionality, one of the biggest selling points for Zen 3. Since X370 motherboards weren't built with PCIe 4.0 in mind, you won't be able to enjoy the fastest SSDs on the market. However, you will have access to Zen 3's prowess though, which ushered in IPC uplifts up to 19%. That alone should be enough incentive to upgrade to the new Ryzen 5000 series. And if you can't afford a new motherboard when doing so, this is at least an option to get things up and running--albeit one you should probably think long and hard about before flashing the board and dropping in your new chip.