As far as I know, Ubuntu and maybe other Linux also are going to drop support for i386.
But if you want to learn how to cross compile to Linux 32-bit from Linux 64-bit, these are things you need to do:
01. You need to instal libc6-dev-i386 package
02. Use a text editor type as --32 $@ and save it as /usr/bin/i386-linux-as
03. Use a text editor type ld -A elf32-i386 $@ and save it as /usr/bin/i386-linux-ld
04. sudo chmod +x /usr/bin/i386-linux-as
05. sudo chmod +x /usr/bin/i386-linux-ld
06. cd /usr/share/fpcsrc/3.0.4
07. sudo make clean all CPU_TARGET=i386
08. sudo make crossinstall OS_TARGET=linux CPU_TARGET=i386 INSTALL_PREFIX=/usr
09. sudo ln -sf /usr/lib/fpc/3.0.4/ppcross386 /usr/bin/ppc386
Note:
You may need to change "3.0.4" (steps #6 and #9) to the version of your FPC.
It is a bit hard to understand the steps above, you need to have some knowledge about Linux Terminal.
You can search the web, all the information to cross compile from Lazarus 64-bit to 32-bit are there.