If you want a large archive for photos that is open source, with the option of self-hosting, you might consider #Piwigo, an option that I took when migrating off #Flickr. https://coevolving.com/blogs/index.php/archive/from-flickr-to-piwigo/ in 2018.
Piwigo has a Social Buttons plugin https://piwigo.org/ext/extension_view.php?eid=673&rid=7992 to share to #Tumblr. I use that for my near-daily photos to https://www.tumblr.com/daviding . The RSS in Tumblr syndicates easily.
Tumblr is now owned by Automattic (developers of #WordPress), and continues to be free of charge. Tumblr is scheduled to support #ActivityPub.
I also post to #Facebook and #Instagram, and occasionally to https://metapixl.com/daviding (#Pixelfed) as an experiment. My primary archive on Piwigo is full resolution photos, that are available as downsampled.
If you don't want to self-host, there's https://piwigo.com/ , @fossheim