I see that the commit 992d0717f06fe12c mentions that the instructions
to build on a board such as a Raspberry Pi are different enough that
adding ARM archs won't work. I'm wondering what's missing here, as it
just built fine on my Raspberry Pi 400 (running Manjaro, aarch64) both
from source, and using the AUR package. Maybe I haven't visited a
complex enough site to break it but it appears to me that it works fine
on ARM boards.

Hi.

From what I found [0] it seems like everything should work fine on
rpi4/400. 
If it works fine for You on rpi4 I guess I can safely add aarch64 to
arch list. 



[0]: https://git.skyjake.fi/skyjake/lagrange#compiling-on-raspberry-pi