Hey Erik,
Not sure if this is still the place to be for ECL questions but here it goes:
Yes, this is the place. Thank you for reporting the problem.
I'm having issues cross-compiling ECL for ARM and since this is actually the first time I'm cross-compiling stuff ever I'm kinda stuck.
Cross-compilation is always a PITA. I'd advise compiling ECL natively on the machine if that is an option.
Problems you encounter are related to the new ECL extension (which was not released yet). This would probably get cought in a few weeks (or months) during testing before the release. I've reported the issue on our tracker (https://gitlab.com/embeddable-common-lisp/ecl/issues/461), you may follow the issue there.
So you are not missing any steps (probably!). You may either use the official release ECL 16.1.3 or wait a few hours (hopefully!) until I fix it (check the mentioned ticket in a few days).
Best regards, Daniel