Very recently on my iPad Pro I have not been able to export RAW photo files from the Photos app to the Lightroom app. Has interrupted my normal editing workflow. The photos will export into LR only as a JPG file with no attached metadata. Have tried fiddling with all settings to no avail. Help!
By default, I think iCloud will upload all your original images to iCloud online storage and keep only downsampled JPG copies on your local device to free up device storage. You can force your device to use the setting "Download and Keep Originals" in iOS Settings > (your name) > iCloud > Photos. My experience is that syncing original images back down from iCloud can take a while (ie., overnight). For more info, see: https://support.apple.com/en-us/HT204264
There is a different iOS setting which I think does not relate exactly to your situation, but I'll mention it anyway in case it helps. In iOS Settings > Photos, there is a Keep Originals option in the section "Transfer to Mac or PC"
Choosing Keep Originals will allow you to export your original images to a desktop computer. I don't think this is relevant exactly to your workflow, but I get the sense that this setting has helped me when I wanted to share or export from the iOS Photos app, sending images to other apps on my device. Photos should be able to share images to Lightroom via the Share options, but really I hope that after your originals are synced from iCloud back to your phone that Lightroom will be able to import as expected from your camera roll.