I try and recognize when a ship, sub, or other missing vessel has been found, especially if it has been missing for a long time. I saw this on Wikipedia today – https://en.wikipedia.org/wiki/French_submarine_Minerve_(S647).
Here are several articles reporting on the sub:
French submarine La Minerve found 50 years after disappearance: https://navaltoday.com/2019/07/22/french-submarine-la-minerve-found-50-years-after-disappearance/.
French submarine found 50 years after disappearance: https://www.theguardian.com/world/2019/jul/22/french-submarine-minerve-found-50-years-after-disappearance
Vessel Finds French Submarine That’s Been Lost for 50 Years: https://www.popularmechanics.com/military/navy-ships/a28472065/minerve-submarine-found/
YouTube (search): https://www.youtube.com/results?search_query=La+Minerve+found+2019
Between the various news reports and articles I read, it appears the sub may have been lost to weather, and based on seismic activity, it likely imploded once it exceeded its depth limit.