Somehow Secure Boot got turned back on during the reinstall lol. I didn’t notice this; disabled secure boot and it boots just fine now. I’ll have to get all my files back on, but yeah, I don’t know of any solution to this issue other than just doing a clean Manjaro reinstall.
Before reinstalling, I did try to do a full system update using chroot in the live iso, but it didn’t change anything unfortunately, so reinstalling did seem to be the easiest solution.