It’s come to our attention that some changes made for KWin in Plasma 6 aren’t compatible with the old and outdated software-rendering graphics drivers in VirtualBox. Thankfully there’s a solution: enable 3D acceleration in the machine settings. It not only resolves the issue, but also enables all the fancy graphical effects you would expect to see on a bare-metal installation. This is especially important if you’re using a VM for a review, screenshots, or videos of Plasma 6!
This is a companion discussion topic for the original entry at https://pointieststick.com/2024/03/08/psa-enable-3d-acceleration-in-your-virtualbox-vms/