So, booting to PureOS did not work completely. I ended up getting a CLI grub output from boot. Using a live Manjaro USB worked. Connecting the M.2 via a USB enclosure did work. In Manjaro everything worked (excepted for the Macbook trackpad and keyboard). Using external peripherals worked. From there, no CLI was needed. Clicking on the home folder and then navigating to an already mounted external drive prompted me with the password for the luks decryption. It worked. Zero issues. I wouldn’t have lost data anyway, but still wanted to be sure.