Dear @vige, you might clarify if a fresh installation of extant apps, which are not explicitly updated for the sandboxing yet, will still be able to create their directories ~/{.local/share,.config,.cache}/packagename and files in it on SailfishOS ≥ 4.3.0?
Currently you only address “configuration files which were already written in .config/harbour-appname”, which supposedly means “before upgrading to SailfishOS 4.3.0”.
Rereading our conversation at the former thread about the topic “configuration and data files of apps with Jolla’s sandboxing” you did not say that all these directories will be creatable and writeable (just “mounted”):
Mind that many apps in the Jolla Store and at Openrepos are not well maintained or unmaintained, although still well working, and if they are not installable any more on recent SailfishOS releases, this will significantly reduce the already slim set of available apps for SailfishOS.
Hence backward compatibility is crucial.