EXIF and XMP metadata is usually embedded into image files. It may also be written to XMP sidecars.
When you check "Tag Masters/Originals", the metadata will be written to the original files rather than being written to preview files showing your latest changes. You almost always want to have this option checked.
When an XMP sidecar is present at the image location, HoudahGeo will read from and write to the sidecar rather than the actual image file. The "Always write XMP sidecar" option forces the creation of an XMP sidecar if none is present. You should uncheck this option.
With the above setup tags will be written where Lightroom can see them. You may verify this by dragging the tagged file into a fresh HoudahGeo project. There you should see the previously added metadata.
You may need to remove XMP sidecars you have previously created using Lightroom.
If you want HoudahGeo to see metadata created by Lightroom, you will need to set your Lightroom catalog to "Automatically write changes to XMP".
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