That was either Void Linux (see sibling comment) or Alpine Linux.
You might also have read Gentoo Linux announcement (https://www.gentoo.org/support/news-items/2021-01-05-libress... ); technically doesn't fit your description since Gentoo never "switched" or "went back", but rather supported them simultaneously, and just pulled support for LibreSSL at some point.
You might also have read Gentoo Linux announcement (https://www.gentoo.org/support/news-items/2021-01-05-libress... ); technically doesn't fit your description since Gentoo never "switched" or "went back", but rather supported them simultaneously, and just pulled support for LibreSSL at some point.