I don't keep a full-fidelity list in my mind of which Debian packages contain every executable because it's easier to relegate that info to outboard-brain tools instead.
For tools that I have locally installed, e.g. ls(1), `dpkg --search "$(which ls)"` (or `dpkg -S "$(which ls)"`) looks up which package owns the tool.
For packages not locally installed, visiting e.g. https://manpages.debian.org/ls#:~:text=Source%20file and then peeking at the "Source file:" page footer shows me the package name.