First create an artful lxc container, it's old enough we can use it to quickly cross-build mono for the older glibc available on Evercades.

sudo lxc launch ubuntu:a/armhf armhf-artful
sudo lxc exec armhf-artful bash

Now let's fix artful's repo situation, this release is outside of the usual repositories due to being too old. We'll then install the packages.

sed -i 's$http://ports.ubuntu.com/ubuntu-ports$http://old-releases.ubuntu.com/ubuntu$' /etc/apt/sources.list
apt update && apt-get install git autoconf libtool automake build-essential gettext cmake python3 curl

Now let's fetch, build and package mono.

wget https://download.mono-project.com/sources/mono/preview/mono-6.12.0.205.tar.xz
tar xf mono-6.12.0.205.tar.xz
cd mono-6.12.0.205
./autogen.sh --with-ikvm-native=no --with-csc=mcs --disable-llvm --disable-dependency-tracking --with-mcs-build --prefix=$(pwd)/built
make -j$(( $(nproc) + 1 )) install 

Notable built fragments:

• bin/mono-sgen, lib/libmono-native.so and lib/libMonoPosixHelper.so: Basic building blocks to run applications.
• DLLs in lib/mono: Can be used to override incompatible versions, mscorlib.dll and mscorlib.dll.so go together.
  • You can easily take a bunch of DLLs automatically with the following hacky script:

#!/bin/bash

gac="mono-6.12.0.205/built/lib/mono/4.5"
FILES=(
"Mono.Posix.dll"
"Mono.Security.dll"
"System.Configuration.dll"
"System.Core.dll"
"System.Data.dll"
"System.Drawing.dll"
"System.Runtime.Serialization.dll"
"System.Security.dll"
"System.Xml.Linq.dll"
"System.Xml.dll"
"System.dll"
"mscorlib.dll"
)

mkdir -p dlls-copy/
for i in "${FILES[@]}"; do
    LINK=$(
        find "$gac" -name "$i" | while read dlllink
        do
            echo $(realpath "$dlllink")
            break
        done
    )

    if [ "x$LINK" == "x" ]; then
        echo "Skipping $LINK"
        continue
    fi

    FILE=$(readlink -f "$LINK")
    echo "Copying $FILE"
    cp $FILE dlls-copy/
done

An example of application being deployed successfully can be seen here: https://github.com/JohnnyonFlame/FNAPatches/releases/tag/shipwreck