Return to Answer

and reinstall it as (real) root user (--reinstall should not even be needed since we just bumped the version):

apt-get install --reinstall ./chromium.deb

The package chromium-l10n can now be installed as usual:

apt install chromium-l10n

and reinstall it as (real) root user, possibly along additional packages (which should be pulled automatically on future upgrades made like this):

apt-get install ./chromium.deb chromium-l10n

If the version wasn't bumped, --reinstall might be needed.

• add (eg below the Architecture: i386 entry) the Multi-Arch: entry:

  Multi-Arch: foreign
  

• edit the Version: entry

  Bump the version by appending a .0 to it. For example today on Debian 12 it would then look like:

  Version: 119.0.6045.123-1~deb12u1.0
  

• edit the Provides: entry (on a package without it, add it):

  Append at the end of it , chromium (= ACTUALVERSION) with ACTUALVERSION replaced by the actual version. For example today on Debian 12 the line would look like:

  Provides: gnome-www-browser, www-browser, chromium (= 119.0.6045.123-1~deb12u1)
  

• add (eg below the Architecture: i386 entry) the Multi-Arch: entry:

  Multi-Arch: foreign
  

• edit the Version: entry

  Bump the version by appending a .0 to it. For example today on Debian 12 it would then look like:

  Version: 119.0.6045.123-1~deb12u1.0
  

• edit the Provides: entry (on a package without it, add it):

  Append at the end of it , chromium (= ACTUALVERSION) with ACTUALVERSION replaced by the actual version without the .0 appended. For example today on Debian 12 the line would look like:

  Provides: gnome-www-browser, www-browser, chromium (= 119.0.6045.123-1~deb12u1)
  

I used to do what OP did with Firefox for the same reasons: sparing memory on a low-end system. The change has to be done in the "main" binary package, not in the packages that depends on it. Also as the package is changed, when keeping the same version, the dependency algorithm will prefer the repository source to the installed source, but won't do it for dependency reasons. It will just always write the package was kept and it won't be easily visible if the package is kept because there's a new version available but not installable, or because it's kept because there's the same version available. This can be worked around requires by slightly increasing the package version.

There's no simple tool to do such change. Personally I edited directly the /var/lib/dpkg/status file which is the database of all installed packages. A mistake there could damage the whole system installation. Below is a longer but safe method.

I used to do what OP did with Firefox for the same reasons: sparing memory on a low-end system. The change has to be done in the "main" binary package, not in the packages that depends on it. Also as the package is changed, when keeping the same version, the dependency algorithm will prefer the repository source to the installed source, but won't do it for dependency reasons. It will just always write the package was kept and it won't be easily visible if the package is kept because there's a new version available but not installable, or because there's the same version available. This can be worked around by slightly increasing the package version.

There's no simple tool to do such change. Personally I edited directly the /var/lib/dpkg/status file which is the database of all installed packages. A mistake there could damage the whole system installation. Below is a longer but safe method: download the binary package, unpack it, edit it as needed and repack it into an alternate binary package and then install this.