Potential solution
1. I installed Java's JRE1.8.0_251 from Java.com

2. I copied C:\Program Files (x86)\Java\jre1.8.0_251 files into C:\Program Files (x86)\Sweet Home 3D\jre8

3. Run Sweet Home 3D 6.3 (from SweetHome3D-6.3-windows.exe)

My PC setup
CPU: Ryzen 9 3900X
GPU: GTX 1080 Ti with driver 446.14 and GeForce Experience disabled. SH3D seems to have a problem with GeForce Experience.
OS: Windows 10 version 2004

My other PC has
CPU: Intel Core i9-9900K
GPU: RTX 2080 Ti with driver 446.14 and GeForce Experience disabled.
OS: Windows 10 version 2004