@britechguy: Thanks for the warning. I suppose you are right. And thanks for the new suggestion too.
Anyway, I am currently backing everything up with Unstoppable Copier. Here's my experience so far :
Unstoppable Copier seems to be the ultimate backup tool I was looking for for a long time, not only for retrieving content from a corrupted drive, but for my regular backups as well. Mainly thanks to its ability to overwrite only older duplicates. Before, I was using Total Commander, which did a fine job at it, but lost time by prompting me in the middle of the night for some issue or other and so pausing until I could respond the next morning ;-)
As for retrieving corrupted files, U.C. provides several options for balancing speed over recovery, and a very clear and verbose real time log. In that respect, it is better than what I was hoping to find.
I've tried playing a copied corrupted video in VLC and observed this: the unplayable portion of the video is longer (2 minutes instead of 30 seconds), as if a big chunk around the fatal corruption had been carved out, but at least it doesn't make VLC crash anymore ! The fact that a bigger chunk is missing may be due to the facts that I set the recovery options to rather fast than good, and I am running U.C. in a virtual Windows machine (so no low-level access to the drive obviously) because I couldn't manage to run the Ubuntu version in Mint.
So, overall, thumbs up. I am quite happy with that solution. (Although now that I think of it, britechguy's solution might get me shorter unplayable parts.)
And if anyone could walk me through running Unstoppable Copier in Linux Mint 19, it would be even better.
If've found out how to run it under regular Ubuntu here : https://tinyapps.org/blog/nix/201008240700_unstoppable_copier_ubuntu.html but that doesn't seem to work under Mint. Just nothing happens when I try opening the program.
Edited by Fredeke, 11 March 2018 - 04:28 AM.