I also use Adobe Lightroom to enter metadata and export via plugin directly towards Piwigo. I started creating a new theme with goal to have metadata displayed correctly. I am not an experienced php developer or Piwigo expert yet (I have experience with other languages), but learning on the fly.

I will describe later on my website how I did it. But currently limited in time to work on it. So now slow progress, but 80% is finished. Expect to have some articles ready in December.

I am in the testing/finetuning/correcting bugs phase. It won't be 100% copy/paste the theme for other users, but also not that complicated if you have some development experience to make changes. There are some specific customisations in the theme, like showing data of scanned images which partly steels info from the filename and pulls info from an XML file.

To fetch metadata from images I use exiftool, so the hosting provider needs to support this (my one does). Data is read from image when displayed and not pulled from database (not best option possibly but works fine on my site). Also relying on some Piwigo plugins.

What I did can be a good starting point for others to use it as base for a Piwigo site. But be patient till I have completed it and have written articles how I did it + making the files available.

Have a look on my site:
https://gallery.fotokruse.eu/
It has images with/without full set of metadata. Scanned photos and photos from my camera.

Regards,
Jan-Willem