I took a stab at upgrading RetroArch using the instructions in this thread, but I ultimately gave up. My device froze during the “make” process and I wasn’t patient enough to start over.
I also tried copying the /usr/local/bin/retroarch binary from OS 0.4 to OS 0.21, but that just caused RetroArch to dump back to the menu. There must be too many unmet dependencies.
I’ll stick with OS 0.21 where I have pixel-perfect rendering for now. Thanks guys!!