All right, I’ve noted the impact of Portainer @driz .
I appreciate Portainer because it allows me to obtain the desired result and configuration very quickly.
I can understand your lack of support due to elements outside the test and qualification environment of your containers.
Copying and pasting templates and adapting them may not be difficult for some but for others it is not so obvious.
I had already read (a while ago, I confess) the readme details of the Sonarr container (for its initialization). But from the logs visible on my first post, I could not see any direct link with my personal variables.
During my tests, I tried to connect to the Sonarr Web UI in HTTP and HTTPS because I know that browsers are now programmed to work in HTTPS by default. But I should have made this point clear.
You could anyway see that TCP port 8989 was quite unavailable although the container responds well to ICMP requests.
But the most important thing is that I finally had the time to test my (very stupid) but strongest hypothesis: simply upgrade my Alpine Linux hosting my containers, including Sonarr.
After a simple
apk upgrade
and a reboot for fun, my Sonarr container is back to life with its data as before.
Thank you all for your support and your investment in my problem 