Random stabs in the direction of developing a usable set of steps to
follow: since you suspect the system may have a problem with i386
packages to begin with, it might be useful to know whether you actually
have any already installed. The first way of finding that out which came
to my mind is:
dpkg -l '*' | grep ':i386'
I do have a few installed, 8 actually, basically libc6:i386 and gcc-8-base:i386 and a few others.
The basic procedure would be an iteration over adding the "will not be
installed" packages (or, in the case of a remove-the-wrong-things
explosion, the important packages that would otherwise be removed)
explicitly to the command line, and repeating with the ones from the
next failure, until it shows you the actual conflict.
Okay, did some of that, the one that really blows up is libicu63:i386, when I try to install that it was to remove most of the amd64 packages.
# apt-cache policy libicu63:i386
stable/main i386 Packages
Compared to it's amd64 package:
# apt-cache policy libicu63
*** 63.1-6+deb10u1 100
stable/main amd64 Packages
if I try to install...
# apt install libicu63:i386
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
acl alsa-utils ant ant-contrib ant-optional at-spi2-core atril-common bubblewrap ca-certificates-java
coinor-libcbc3 coinor-libcgl1 coinor-libclp1 coinor-libcoinmp1v5 coinor-libcoinutils3v5
etc etc etc