There’s another Linux ext2 file system for UEFI being worked on:
Uefi-Ext2-Reader: This is a project for System Software subject for my study in Gdansk University of Technology. UEFI supports only Windows FAT file system. I implemented a protocol that allows to read files from Linux Ext2 partition in UEFI. I used VisualUEFI (https://github.com/ionescu007/VisualUefi.git) for compiling process.