A minimal example that renders "Hello World" on the reMarkable with QT using the original toolchain.
This is a simplified version of https://github.com/reHackable/reHackable-HelloWorld.
The build steps are quite simple (they are based on the excellent build instructions from draft
Get the reMarkable toolchain install script from https://remarkable.engineering/oecore-x86_64-cortexa9hf-neon-toolchain-zero-gravitas-1.8-23.9.2019.sh and install the toolchain. Once installed, activate the environment in within your terminal instance via source <path-to-installed-toolchain/environment-setup-cortexa9hf-neon-oe-linux-gnueabi. Now you can run qmake && make and copy over the files reHackable-launcher and Main.qml to your reMarkable.
$ wget https://remarkable.engineering/oecore-x86_64-cortexa9hf-neon-toolchain-zero-gravitas-1.8-23.9.2019.sh
$ chmod +x ./oecore-x86_64-cortexa9hf-neon-toolchain-zero-gravitas-1.8-23.9.2019.sh
$ ./oecore-x86_64-cortexa9hf-neon-toolchain-zero-gravitas-1.8-23.9.2019.sh
$ source <path-to-installed-toolchain/environment-setup-cortexa9hf-neon-oe-linux-gnueabi`
$ qmake && make
$ scp minimal-render Main.qml 10.11.99.1