Panel Self Refresh (PSR), a power saving feature used by Intel iGPUs is known to cause flickering in some instances FS#49628 FS#49371 FS#50605. A temporary solution is to disable this feature using the kernel parameter i915.enable_psr=0 or xe.enable_psr=0.
i915.enable_psr=0 to your GRUB boot parameters (usually in /etc/default/grub under GRUB_CMDLINE_LINUX_DEFAULT).intel_iommu=igfx_off to the GRUB command line.i915.enable_fbc=0 to boot parameters.intel_idle.max_cstate=2 to the kernel boot parameters.