Thank you for your feedback!
You could try lowering the graphics in the settings menu. When I turn off SSAO, AA and shadows on my laptop, the game runs with 90+ fps on integrated graphics. There's also a new lightweight 2D client in development, which is optimized for low-end devices such as the Librem 5.
We did use an asset pack as a basis, but many of the models, textures and sounds are original and were made specifically for this project.
We are also planning to continue adding features to the game in the future!