Puisque ça a marché pour Borg, je tente de forcer un upgrade :
$ sudo yunohost app upgrade etherpad_mypads --force
Info: Now upgrading etherpad_mypads...
Info: [+...................] > Loading installation settings...
Info: [#...................] > Checking version...
Warning: (this may take some time)
Info: The service etherpad_mypads has correctly executed the action restart.
Info: [#+++................] > Backing up the app before upgrading (may take a while)...
Info: [####................] > Activating maintenance mode...
Info: [####................] > Stopping a systemd service...
Info: [####................] > Ensuring downward compatibility...
Info: [####................] > Making sure dedicated system user exists...
Info: [####+...............] > Upgrading source files...
Info: [#####...............] > Upgrading dependencies...
Warning: dpkg: warning: version 'v7.5.0' has bad syntax: version number does not start with digit
Info: [#####...............] > Upgrading NGINX web server configuration...
Info: [#####...............] > Configuring log rotation...
Info: [#####+..............] > Reconfiguring Etherpad...
Info: [######..............] > Upgrading systemd configuration...
Info: [######+++++++.......] > Installing Etherpad plugins...
Info: [#############++++...] > Upgrading Etherpad...
Info: [#################+..] > Upgrading logrotate configuration...
Info: [##################..] > Integrating service in YunoHost...
Info: [##################..] > Starting a systemd service...
Warning: (this may take some time)
Info: The service etherpad_mypads has correctly executed the action restart.
Info: [##################+.] > Reconfiguring Fail2Ban...
Info: The service fail2ban has correctly executed the action reload-or-restart.
Info: [###################.] > Reloading NGINX web server...
Info: [###################.] > Disabling maintenance mode...
Info: [####################] > Upgrade of etherpad_mypads completed
Success! etherpad_mypads upgraded
Success! Upgrade complete
Ça a marché, j’ai de nouveau un etherpad fonctionnel! (Bien que je le trouve toujours un peu lent, mais ça c’est peut-être à cause du serveur…)