So I was indeed able to recover my system by changing the symlink in /lib64/ with an emergency USB key. For the record, after shutdown, the system of course would not come up. I am afraid that people with less patience than I would conclude that their system was hopelessly ruined.
However, I have one issue remaining: what to do now with the half-installed state of libc6-amd64. Trivially, I don't trust removing libc6-amd64 will do the right thing and currently apt is blocked by the state of libc6-amd64. I thought reinstalling libc6-amd64 would at least keep apt happy, but no. paul@wollumbin ~/motif/debian-pkg-xshisen $ sudo apt-get install libc6-amd64 Reading package lists... Done Building dependency tree Reading state information... Done libc6-amd64:i386 is already the newest version. libc6-amd64:i386 set to manually installed. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. Need to get 0 B/4,393 kB of archives. After this operation, 0 B of additional disk space will be used. Do you want to continue [Y/n]? dpkg: error processing libc6-amd64 (--configure): package libc6-amd64 is not ready for configuration cannot configure (current status `half-installed') Errors were encountered while processing: libc6-amd64 E: Sub-process /usr/bin/dpkg returned an error code (1) Advice is welcome.
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