# apt install zstd:alpha
...
...
The following NEW packages will be installed:
  gcc-10-base:alpha libc6.1:alpha libcrypt1:alpha libgcc-s1:alpha libidn2-0:alpha liblz4-1:alpha liblzma5:alpha libstdc++6:alpha libunistring2:alpha
  zlib1g:alpha zstd:alpha
...
...
Do you want to continue? [Y/n]
Preconfiguring packages ...
Selecting previously unselected package gcc-10-base:alpha.
(Reading database ... 744802 files and directories currently installed.)
Preparing to unpack .../00-gcc-10-base_10.2.0-18_alpha.deb ...
Unpacking gcc-10-base:alpha (10.2.0-18) ...
Selecting previously unselected package libgcc-s1:alpha.
Preparing to unpack .../01-libgcc-s1_10.2.0-18_alpha.deb ...
Unpacking libgcc-s1:alpha (10.2.0-18) ...
Selecting previously unselected package libc6.1:alpha.
Preparing to unpack .../02-libc6.1_2.31-3_alpha.deb ...
Unpacking libc6.1:alpha (2.31-3) ...
dpkg: error processing archive /tmp/apt-dpkg-install-vYR8wY/02-libc6.1_2.31-3_alpha.deb (--unpack):
 trying to overwrite '/lib/ld-linux.so.2', which is also in package libc6:i386 2.31-4
Selecting previously unselected package libcrypt1:alpha.
Preparing to unpack .../03-libcrypt1_1%3a4.4.17-1_alpha.deb ...
Unpacking libcrypt1:alpha (1:4.4.17-1) ...
Selecting previously unselected package libunistring2:alpha.
Preparing to unpack .../04-libunistring2_0.9.10-4_alpha.deb ...
Unpacking libunistring2:alpha (0.9.10-4) ...
Selecting previously unselected package libidn2-0:alpha.
Preparing to unpack .../05-libidn2-0_2.3.0-4_alpha.deb ...
Unpacking libidn2-0:alpha (2.3.0-4) ...
Selecting previously unselected package liblz4-1:alpha.
Preparing to unpack .../06-liblz4-1_1.9.2-2_alpha.deb ...
Unpacking liblz4-1:alpha (1.9.2-2) ...
Selecting previously unselected package liblzma5:alpha.
Preparing to unpack .../07-liblzma5_5.2.4-1+b1_alpha.deb ...
Unpacking liblzma5:alpha (5.2.4-1+b1) ...
Selecting previously unselected package libstdc++6:alpha.
Preparing to unpack .../08-libstdc++6_10.2.0-18_alpha.deb ...
Unpacking libstdc++6:alpha (10.2.0-18) ...
Selecting previously unselected package zlib1g:alpha.
Preparing to unpack .../09-zlib1g_1%3a1.2.11.dfsg-2_alpha.deb ...
Unpacking zlib1g:alpha (1:1.2.11.dfsg-2) ...
Selecting previously unselected package zstd:alpha.
Preparing to unpack .../10-zstd_1.4.5+dfsg-4_alpha.deb ...
Unpacking zstd:alpha (1.4.5+dfsg-4) over (1.4.5+dfsg-4) ...
Errors were encountered while processing:
 /tmp/apt-dpkg-install-vYR8wY/02-libc6.1_2.31-3_alpha.deb
needrestart is being skipped since dpkg has failed
E: Sub-process /usr/bin/dpkg returned an error code (1)
#


(please don't ask why).

Control: reassign -1 src:glibc 2.31-3

libc6.1 only exists in debports, reassigning to the source package in
unstable.

Kind regards,
Andrei