[jpetso]

Qt hasn't been terrible in terms of upgradeability between major versions for many use cases, but Krita got the short end of the stick.

Krita's scope and architecture requires both cross-platform compatibility and deep integration with the OS. For the latter, they need some degree of going past Qt's cross-platform abstractions, and Qt happens to have made some substantial changes to the way they build on the platform's graphics APIs.

As long as you're sticking with Qt's cross-platform API, you're good; if you ignore it and go full OpenGL or Vulkan for all UI, you're good; it's when you try to mix both that things get hairy.

[yosefk]

By going full Vulkan, you mean do nothing at all in Qt, or do you mean a particular way to use Qt but not some parts of it?