Here is a link to a description of how to transfer an album in FotoAlbum to hosting on piwigo whilst (hopefully) maintaining any associated captions
drive.google.com
I am still leaning various complexities and this linked file will be updated with new information and improvements as I glean it.
Although this description is specific to home hosted Piwigo on a Raspberry Pi, hosting sites which do Piwigo appear to be available and all software generated is in portable languages (i.e web servers, SQLite, mysql) so basic principles could be transferrable to other platforms.