After many years of hosting photography on 3rd party sites, subject to their cluttered designs, overbearing social mechanisms and occasionally questionable licences - I decided to go it alone and host my own work with no mess, no distractions.
Vanity produces a lean, compact, static website where the focus is solely on the images.
I use it for my own gallery, photography.ishani.org, but it wouldn't be difficult to bend into another shape should you want to use it for your own.
Vanity accepts an arbitrarily-deep folder hierarchy of images, per-gallery JSON configuration metadata and produces high-quality thumbnails and a set of minified HTML files using T4 templating.
The theme uses Bootstrap 4 and PhotoSwipe to provide a minimalist interface that works on any device.
Vanity uses jpegoptim64 to strip and pack resulting JPEGs. It doesn't change any of the input images.
It's somewhat optimised (doesn't do work if it can avoid it) and pretty well tested (in use for over 3 years now) but YMMV - to customize it, you can fiddle with the 3 T4 files and single stylesheet fairly easily.