App sandboxing is less of a concern when the software you use is built from source in your distro's package repository, and is maintained by distro maintainers whose interests align more closely to yours than the software manufacturer's. Ironically, Flatpaks are software from upstream and thus harder to trust.
My comment is very clearly about open-source software, yes. Also for photo editing and video editing there is open-source software, and there's no reason for Debian to not package it.
In any case, "any software may be tracking the Linux user" is an exaggeration. The vast majority of software on the average Linux user's desktop is open-source software from their distro repo.
