Microsoft released the list of processors supported by Windows 10 May 2019 Update. There is no change from the previous upgrade. Ryzen 3000 is currently not supported.
Windows 10 v1903 RTM or May 2019 Update is currently available in the Windows Internal Review Preview Ring. Microsoft said the tests were scheduled for one month to resolve the latest errors and improve performance.
As for the list of supported processors, nothing has changed since the October 2018 upgrade (Windows 10 v1809). It includes all Intel processors up to the 9th Core, Intel Xeon E-21xx, Intel Atom (J4xxx / J5xxx and N4xxx / N5xxx), Celeron and Pentium. At AMD we have all-to-seventh generation chips (A-Series Ax-9xxx and E-series Ex-9xxx & FX-9xxx), Athlon 2xx, Ryzen 3/5/7 2xxx, Opteron and EPYC 7xxx and Qualcomm Snapdragon 850 support.
Windows 10 v1903, not the Ryzen 3000 series.
Currently, no Qualcomm Snapdragon 8cx is mentioned in this list. Its launch is scheduled for later, its support will probably be part of the new Windows 10 19H2. The AMD series Ryzen 3000 is also not mentioned. As this upgrade is not yet available, it is likely that the list will grow in the coming weeks.
After all, if your computer is already running Windows 10 v1809, it will not have problems with Windows 10 v1903. The basic requirements for installing Windows 10 on a computer require a 1 GHz or faster processor, 1 GB RAM (32-bit) or 2 GB (64-bit), 16 GB storage space for 32-bit or 32-GB for a 64-bit system and a graphics solution compatible with DirectX 9 or later with WDDM 1.0 driver