So I ported the C code from the Raspberry Pi library for the e-paper to the NodeMCU firmware. The source code didn't look very nice, I refactored and cleaned it a bit. I'm using strings for the binary image data, because this needs less memory than arrays in Lua. But I get "string length overflow" error.

Turns out the default max string length in Lua for NodeMCU is 4096 bytes, and of course Murphy says I need 5808 bytes to store an image for my e-paper. But at least it can be changed with collectgarbage("setmemlimit", kilobytes) at runtime. Too bad there is only about 40 kB usable SRAM. I guess sooner or later I need to buy an ESP32, which has 520 kB.