LED matrices with SPI (chip MAX7219) are rather cheap and my worked without level converters with Raspberry Pi even if it was for Arduino, since it is just output, and 3.3 V is interpreted as logic one. I have developed an AA powered portable game for 8x8 LED matrix connected to a Raspberry Pi with five wires (SPI). English video:
https://youtu.be/O5Xhr-NHvAw . Swedish (svenska) video:
https://youtu.be/A5NT93l-vrI . Video with the earlier curses version:
https://youtu.be/RkcHImd9MX0 . The project is on GitHub with GPLv3 license:
https://github.com/mobluse/blockis . The game Blockis is similar to Tetris.