Canon 5d mark 4 Can't upload raw images to Lightroom 5

Not much, I'm afraid. The 5D Mk 4 requires Lightroom 6.7 or later to process raw files, but Lightroom 6.x is no longer available, so the only route forward would be by purchasing an Adobe subscription for Lightroom Classic. However, Lightroom Classic will not run on that very old operating system. The alternative to a subscription would normally be the free Adobe DNG converter (i.e. standalone program to convert the raw files to the DNG format, which LR5 could then read), but the same software restriction applies as the current DNG converter requires MacOS 10.15 or later.

So your options are very limited. If you want to stay with Lightroom, and you want to shoot Raw with your new camera, then you would need to upgrade your laptop and take out a subscription plan for Lightroom Classic. Alternatively, it might be possible to use Canon's DPP software to convert your raw files to Tiff for import to LR5, but that's assuming that DPP itself will still run on that old Mac software.