yurets_z, you seem to be getting a bit of a roasting here, I have no idea why. Thaddy is always rude to people, please disregard him. Please don't judge us all by this exchange.
It does seem you downloaded exactly what you should have, the readme for it says -
This snapshot fpc-3.3.1.riscv64-linux.built.on.x86_64-linux.tar.gz was generated 2026-01-14 12:14 on gcc421 using:
make singlezipinstall OS_TARGET=linux CPU_TARGET=riscv64 SNAPSHOT=1 "BUILDFULLNATIVE=1 BUILDFULLNATIVE=1" PP=ppcx64 CROSSOPT="-XR/home/muller/sys-root/riscv64-linux -Fl/home/muller/sys-root/riscv64-linux/usr/lib64/lp64d -Fl=/home/muller/sys-root/riscv64-linux//usr/lib64/lp64d -Fl/home/muller/sys-root/riscv64-linux/usr/lib64/lp64 -Xd -k--sysroot=/home/muller/sys-root/riscv64-linux -dXr_disabled" OPT=""
I have never used those installers but looks like a good thing !
So, you are planning to run Lazarus (and FPC) on the SBC to do development work there ? If so, you would be better to build a RISC-V64 compiler, not a cross compiler. Move it to the SBC and then run your Lazarus build there (if it has enough memory).
Alternatively, if you plan to develop on your x86_64 box and cross compile then you don't need to build Lazarus with the cross compiler, just build (or install) a standard Lazarus and set a project mode to use your cross compiler from within the IDE. The IDE just does IDE stuff, it passes the compiling to what ever compiler is necessary.
So, question, do you have an x86_64 compiler on your x86_64 machine ? The cross compiler you downloaded is not enough to build Lazarus.
Davo