I'm just going to drop this here, mostly so I don't forget. If you try to install octoprint from scratch on Alpine Linux or another random linux distro, and you get the following error when it tries to build netifaces:
netifaces.c: In function 'gateways':
netifaces.c:1808:9: error: initialization of 'int' from 'void *' makes integer from pointer without a cast [-Wint-conversion]
1808 | NULL,
| ^~~~
netifaces.c:1808:9: note: (near initialization for 'msghdr.__pad1')
you can get it to install with
(venv) ~/Octoprint # CFLAGS="-Wno-int-conversion" pip install netifaces
That turns the error into a warning, and lets it go. Not sure why Alpine's gcc is so picky by default, but there we are.