Having spent a significant amount of time resolving this, I’m sharing the solution here.
When selecting the Wayland session on Ubuntu 24.04 with proprietary NVIDIA drivers, you might find yourself stuck with software rendering in GNOME Shell.
The root of the issue is an outdated libnvidia-egl-wayland1 package, which is version 1.1.13 in the default repositories. Upgrading it to version 1.1.17 from the graphics drivers PPA will enable proper hardware-accelerated Wayland.
A remaining caveat is that this package is still outdated for Snap applications, causing them (e.g., Firefox) to fall back to software rendering. But this can be resolved eventually.
However, note that the Wayland session for NVIDIA was primarily meant for testing in Ubuntu 24.04 instead of productive use.