Use this to update a game's FNA installation!

fnaUpdate.sh

#!/bin/bash
# FNA Update Script
# Written by Ethan "flibitijibibo" Lee
#
# Released under public domain.
# No warranty implied; use at your own risk.
#
# Run this script in the game's executable folder.
#
# This script requires the following programs:
# - git
# - msbuild, which should include a C# compiler
#
# You may want to update MonoKickstart as well!
# https://github.com/flibitijibibo/MonoKickstart/tree/master/precompiled

# Be Smart. Be Safe.
set -e

# Move to script's directory
cd "`dirname "$0"`"

# Grab native libraries
curl -O https://fna.flibitijibibo.com/archive/fnalibs.tar.bz2
tar xvfj fnalibs.tar.bz2 lib64
rm fnalibs.tar.bz2 # Wouldn't want to waste disk space, would we...

# Download and build latest FNA
if [ -d "FNA" ]; then
	cd FNA
	git pull
	git submodule update
else
	git clone --recursive https://github.com/FNA-XNA/FNA
	cd FNA
	curl -o FNA.Settings.props https://flibitijibibo.com/Terraria.Settings.props
fi
msbuild /p:Configuration=Release /p:Platform=x86 FNA.sln
cd ..
cp FNA/bin/Release/* .

# We out.
echo Complete!

This works fine for Terraria but not as well for tModLoader.

I tried using this for tModLoader, but it seems they use a modified version of FNA. As a result, using the FNA.dll built by this script crashes the game.

You can replace the libraries without any issues though. Run the script in an empty folder. Once the libraries are built (specifically, libFNA3D.so.0, libFAudio.so.0, libSDL2-2.0.so.0, and libtheorafile.so, saved in /lib64), copy them to /tModLoader/Libraries/Native/Linux/. It won't crash if you don't replace FNA.dll. However, I’m not sure if tModLoader's libraries are outdated, so replacing them might not have any effect.

fnalibs.tar.bz2 do not seem to be part of that flibitijibibo archive link anymore, but rather this link:
https://github.com/FNA-XNA/fnalibs-dailies/actions

this should probably be updated