Best solution
Since I also upgraded my old Acer Swift One to 24.04 but the "better solution" did not work, I had to fall back on the first mentioned solution.
It works perfectly but I deemed it unacceptable for a laptop because of battery life. So I kept on searching for a solution that, besides solving the problem, also behaves a bit more battery friendly and I found what I was looking for:
Use this instead of the line mentioned in the previous post:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_iommu=igfx_off"
The only drawback is that the GPU no longer can provide GPU-passthrough under virtualisation, which is (in my usecase) perfectly acceptable.