Upgrade to Windows 10 feature 2004 broke AMD driver. System reverted to Windows basic driver. Installed latest AMD driver successfully, but terrible pointer and text cursor lag. Pointer pauses for half a second before catching up with the mouse, then draws pointer for about half a second, then pauses, and jumps to the new mouse location. Makes pointer unusable. Text cursor pauses keystroke display so badly it is not possible to describe exactly what happens, but it makes keystroke input very difficult.
Rolling back driver to Windows basic driver solves both problems, as does rolling back the windows update to 10.0.18363 Build 18363 and keeping the latest AMD driver.
All on a vanilla Dell Inspiron 27 7775 with an AMD Ryzen 7 1700 8-core 3000 Mhz processor.