Also, I remember some issue with external monitors on this list not long ago: https://lists.archlinux.org/pipermail/arch-general/2019-June/046539.html Even if the OP suspected a faulty HDMI port, this might still be related.There are *some* issues with intel gpu's and recent kernels. I can't use multiple monitors in most of the cases as the i915 module misinterpret possible resolutions, for example.
