I tried this in macOS. It looks like the check for exiftool does not work correctly. Can you change line 132 in the Lua script contrib/website_gallery_export.lua to this?
if exiftool == true then
Or apply this patch:
--- a/contrib/website_gallery_export.lua
+++ b/contrib/website_gallery_export.lua
@@ -129,7 +129,7 @@ local function fill_gallery_table(images_ordered, images_table, title, dest_dir,
dt.print(_("export thumbnail image ") .. index .. "/" .. #images_ordered)
write_image(image, dest_dir, filename)
- if exiftool then
+ if exiftool == true then
width, height = exiftool_get_image_dimensions(df.sanitize_filename(dest_dir .. PS .. "images" .. PS .. get_file_name(filename)))
else
width = sizes[index].width
After this change, the export works fine here using darktable 5.2.1 on macOS.