Maybe at least try https://codeberg.org/thirtysix/painterest

Short answer, no. There isn't any FOSS image search with own index or at least only use the images from certain webs, like Pinterest, Pixabay and similar, there are only valid extensions which are FOSS using the index from Google, Bing, Yandex and others, like eg. the one I use https://github.com/dessant/search-by-image (Extension from Germany)