French Minerve submarine is found after disappearing in 1968
bbc.com
bbc.com
The ship used is the Seabed Constructor: https://www.swireseabed.com/assets/vessels/seabed-constructo...
And there is commercial info in Ocean Infinity official website: https://oceaninfinity.com/
do you really think military intelligence would always release information in these cases?
money down, 9/10 times in cases like these someone protecting a source or hiding some knowledge for sigint/opsec/? purposes
http://www.iusscaa.org/articles/brucerule/
As another person upthread noted, though, it is difficult to ever know with certainty not only due to the technical limitations but also due to the opsec limitations.