After several issues with SH3D 5.2 on Linux (Graphical issues and crashes with WebStart, long startup time with installer), I'm glad to see after some testing that the 5.3 release supposes to be much stabler on Linux.
I can confirm the notable performance decrease - although more related to the plan instead to 3D. In fact, it's not really usable anymore from an UX perspective. So I'll unfortunately have to continue with 5.2 for now

However, awesome product!