I’m impressed that QT runs clean enough under ubsan for daily use.

ubsan definitely has some warnings due to a few "technically UB" patterns used as optimizations in Qt as they are known-working on every target platform under the sun, but yeah, no crashes :)

I'm only using this configuration for the software I develop though (+ libc++ debug mode) as it's painfully slow, but it exercises the Qt codebase in depth.