It’s an ongoing bug in 5.x which you can workaround on a source build by recompiling llbEmbree with a flag which allows invalid rays during lighting builds. (the setting is called something like IGNORE_INVALID_RAYS) which you want to set to true/yes
there’s a build script somewhere in Engine/Source/ThirdParty/Intel/Embree which should have a setting for that flag. (last time i’ve tried that Unreal used embree 2140 even if there are more recent versions in there)
after rebuilding the libraries you have to replace the ones in the Engine binaries (search for the .so files that are in the build directory and just copy them over, or link to them)
What i would recommend instead is to take a look at those patches:
they enable GPU Lightmass for Vulkan and they work on Linux, bypassing libembree and the issue you are facing above, while you get faster light build times because it happens on the GPU