When attempting to install, I received the following message:

******************************************************************************
*
* The usr-is-merged package cannot be installed because this system does
* not have a merged /usr.
*
* Please install the usrmerge package to convert this system to merged-/usr.
*
* For more information please read https://wiki.debian.org/UsrMerge.
*
******************************************************************************

This despite the fact that I have version 39 of usrmerge installed, and the
symlinks were indeed set up correctly.

In the end, it turned out to be because /usr itself was a symlink, and
although this causes no issues for either the merging process or any
running software, since the check is using "readlink -f" it erroneously
fails.

Control: tags -1 moreinfo

Why is /usr a symlink? How did you install your debian system?

It's something I set up manually 15 years ago or something, to deal with a
situation where /usr plus some other static directories needed to live on a
different hard drive. Different times...

Obviously not something any installer will ever do, but I don't think it's
against policy? Given that packages depend on usr-is-merged to signal
proper merged state, it shouldn't force you to undo that (especially given
that it's a very risky/tricky operation).

Control: tag -1 wontfix
I understand the issue, but right now I cannot see a simple way to
make the check work with your setup.
Development of usrmerge started 10 years ago and the program will be
retired with the next Debian release: at this point I do not feel like
introducing major changes anymore for marginal use cases.

You can easily rename /usr by installing busybox-static and then running
"busybox ash": you will get a shell which magically uses all the
busybox built-in commands.

Yeah, I moved /usr quite a while ago. IIRC things went sideways halfway
through and I ended up needing to manually run mv with ld-linux.so and
LD_LIBRARY_PATH, but it got fixed eventually.

Dear submitter,

as the package usrmerge has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1088212

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Paul Tagliamonte (the ftpmaster behind the curtain)