Bonjour nizarus,
Bienvenu au forum!
Tant pis que le mise a jour a une erreur
Je peux lire Francais, mais ecrire la est un probleme (pour coux qui lirez
), je continue au Anglais 
2023-12-15 10:14:52,787: DEBUG - + NO_BACKUP_UPGRADE=1
2023-12-15 10:14:52,787: DEBUG - + ynh_print_warn '--message=$NO_BACKUP_UPGRADE is set, backup will be avoided. Be careful, this upgrade is going to be operated without a security backup'
2023-12-15 10:14:52,789: INFO - [##+.................] > Backing up the app before upgrading (may take a while)...
2023-12-15 10:14:52,795: DEBUG - + ynh_print_log '$NO_BACKUP_UPGRADE is set, backup will be avoided. Be careful, this upgrade is going to be operated without a security backup'
Did you turn off backups on purpose? Do you have a backup separate from the update process?
Unfortunately, it seems that a backup also would not have helped. I noticed another member posting that they had a problem upgrading, and their backup would not restore.
I wondered if more people got a problem; searching revealed that last week some people had problems installing Mastodon.
The problem when installing had to do with Ruby and is maybe corrected now (I did not check), but maybe the solution (built ruby-something) does not work with an existing installation; your log (and the others upgrading) have these lines with a warning:
2023-12-15 10:17:32,751: DEBUG - + ynh_ruby_try_bash_extension
2023-12-15 10:17:32,751: DEBUG - + '[' -x src/configure ']'
2023-12-15 10:17:32,751: DEBUG - + src/configure
2023-12-15 10:17:32,754: DEBUG - + make -C src
2023-12-15 10:17:32,755: DEBUG - make: Entering directory '/opt/rbenv/src'
2023-12-15 10:17:32,756: DEBUG - Warning: this Makefile is obsolete and kept only for backwards compatibility.
2023-12-15 10:17:32,757: DEBUG - You can remove the `configure && make ...' step from your rbenv setup.
2023-12-15 10:17:32,757: DEBUG - make: Leaving directory '/opt/rbenv/src'
Maybe it has nothing to do with the failure, but it is the only thing that seems close to anything resembling an error.
With what I know about Mastodon I can’t help you any further, I hope someone else comes along with a good suggestion!