Hi, i want upgrade 16.0 to 21 but with softaculous but :
Les erreurs suivantes ont été trouvées :
It is not possible to Upgrade from 16.0.3 to 21.0.1
Please upgrade to the 20.0 version before upgrading to 21.0.1
Where is 20.0 and when upgrade please
normally you update version by version.
16 → 17 → 18 → 19 → 20 → 21
Skipping major updates isn’t supported as @Reiner_Nippes already mentioned. Please keep in mind that it might also be necessary to update to a newer PHP version before you can upgrade Nextcloud. So please check the system requirements BEFORE each version update 
Yes but Softaculous (Cpanel) want upgrade 21, no 17 or 20…
It does not offer to install or uprade old versions
Yes softaculous check this for me and i upgrade PHP version
Better would be a new installation 
bug in cpanel? or a magic script that handles all steps in the bckground for you.