As described in https://github.com/prusa3d/PrusaSlicer/issues/6396
At startup, the 3D view is not rendered and the underlying background is left visible. The application remains responsive and can be closed normally. On the command line, it reports a series of
[(timestamp)] [0x0000000806012000] [error] Unable to init glew library
FreeBSD thorium 13.0-RELEASE FreeBSD 13.0-RELEASE #0 releng/13.0-n244733-ea31abc261f: Fri Apr 9 04:24:09 UTC 2021 firstname.lastname@example.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64
Name : PrusaSlicer
Version : 2.3.0_4
Installed on : Fri May 7 22:13:56 2021 CEST
Origin : cad/PrusaSlicer
Architecture : FreeBSD:13:amd64
Created attachment 224841 [details]
Seems, it;s a bug of wxWidget 3.1.5? current head is already fixed.
I found only ugly hack which fixes the problem but I don't intend to suggest to commit.
BTW, the same problem there is in new 2.3.1 version of PrusaSlicer, which I suggested to commit ( https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255363 )