=> But Qt 5.12.2 doesn't come with WinGW 32 bits.
=> No it doesn't work in Qt Creator either. In Qt Creator, I only get a message "Application crashed". I get the error code only when launching the executable manually.
The wiki page says, "This guide... assumes that... the release version of your app works correctly when you build + run it from Qt Creator".
If it doesn't work in Qt Creator, then it won't work when you try to deploy it.
Create a small Hello World project using Qt only. Does this run correctly in Qt Creator? Create a small project that uses your external lib. Does this run correctly in Qt Creator?
As I said I am using 32bits external libs. Maybe the issue is with those libs. Could you give me a pointer on how to try to debug this?