This may or may not be useful to you:

The 4.0.0-beta1.1 x86_64 .appimage file on Linux shows the crash failure and charactersistics as described by alvinwong for Windows.

The differences going from 4.0.0 to 4.1.0 and/or from Linux to Windows may be a pointer for you.

Hm... I've checked, and I don't get a crash with that appimage either.

boudewijn wrote:Maybe we should update the frameworks libraries then... But I am loth to do that before the release. I think it would be better to just hide the action on Windows.

Nah, not for 4.0 release at least. We can try it on master after the other 4.0 release stuff is done.

My observation was for running the 4.0.0-beta1.1-x86_64 appimage on debian 9, with configuration/etc files and folders from Krita 3.3.3 already in place.

I removed all Krita files and folders to give 4.0.0-beta1.1 a clean start and it still showed the crash behaviour as noted.

Could there be any benefit in investigating this situation and arrangement any further?

EDIT: It just got interesting: I tried it on Linux Mint 18.3 and it is fine and has a sets of 'special characters' in the Insert Special Character sub-window. It may be due to the lack of installation of certain character fonts in the OS or some lack of method of availability to Krita?
The 'Character Map' utility in Debian 9 MATE does seem to be less comprehensive in content than the equivalent utility in Linux Mint MATE.