mate-sensors-applet has previously been forked to not suggest a package which in Debian contains nonfree code (see T222).
PureOS however do not ship nonfree packages, and the suggestion is therefore - in the context of PureOS - not promotion of nonfree software but merely "promotion" of non-existing (and therefore undefined regarding freedoms) software.
Please reset to again track the Debian-shipped mcomix package.