tj@hephaestion:/var/lib/dpkg$ sudo apt install libunwind8:i386
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libnspr4:i386 libnss3:i386 libsctp1:i386 lksctp-tools:i386 watershed
Use 'sudo apt autoremove' to remove them.
The following packages will be upgraded:
  libunwind8:i386
1 to upgrade, 0 to newly install, 0 to remove and 1 not to upgrade.
Need to get 46.4 kB of archives.
After this operation, 1,024 B disk space will be freed.
Get:1 http://gb.archive.ubuntu.com/ubuntu xenial/main i386 libunwind8 i386 1.1-4.1 [46.4 kB]
Fetched 46.4 kB in 0s (157 kB/s)     
dpkg: error processing archive /var/cache/apt/archives/libunwind8_1.1-4.1_i386.deb (--unpack):
 libunwind8:i386 1.1-4.1 (Multi-Arch: no) is not co-installable with libunwind8 which has multiple installed instances
Errors were encountered while processing:
 /var/cache/apt/archives/libunwind8_1.1-4.1_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)