I'm trying to install libssl-dev for the armhf architecture on a x86_64 system for cross-compilation. Here is what I have done:
$ sudo dpkg --add-architecture armhf
$ sudo apt update
Hit:1 https://deb.nodesource.com/node_10.x bionic InRelease
Hit:2 https://dl.yarnpkg.com/debian stable InRelease
Hit:3 http://archive.ubuntu.com/ubuntu bionic InRelease
Get:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:5 http://security.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Get:6 https://deb.nodesource.com/node_10.x bionic/main armhf Packages [765 B]
Get:7 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:8 https://dl.yarnpkg.com/debian stable/main armhf Packages [7905 B]
Ign:9 http://archive.ubuntu.com/ubuntu bionic/main armhf Packages
Ign:10 http://archive.ubuntu.com/ubuntu bionic/restricted armhf Packages
Ign:11 http://archive.ubuntu.com/ubuntu bionic/universe armhf Packages
Ign:12 http://archive.ubuntu.com/ubuntu bionic/multiverse armhf Packages
Ign:9 http://archive.ubuntu.com/ubuntu bionic/main armhf Packages
Ign:10 http://archive.ubuntu.com/ubuntu bionic/restricted armhf Packages
Ign:11 http://archive.ubuntu.com/ubuntu bionic/universe armhf Packages
Ign:12 http://archive.ubuntu.com/ubuntu bionic/multiverse armhf Packages
Get:13 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [414 kB]
Ign:14 http://security.ubuntu.com/ubuntu bionic-security/main armhf Packages
Get:15 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [90.1 kB]
Ign:16 http://security.ubuntu.com/ubuntu bionic-security/universe armhf Packages
Get:17 http://security.ubuntu.com/ubuntu bionic-security/universe Translation-en [48.9 kB]
Ign:18 http://security.ubuntu.com/ubuntu bionic-security/multiverse armhf Packages
Ign:19 http://archive.ubuntu.com/ubuntu bionic-updates/main armhf Packages
Ign:14 http://security.ubuntu.com/ubuntu bionic-security/main armhf Packages
Get:20 http://archive.ubuntu.com/ubuntu bionic-updates/main Translation-en [154 kB]
Ign:16 http://security.ubuntu.com/ubuntu bionic-security/universe armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu bionic-security/multiverse armhf Packages
Ign:14 http://security.ubuntu.com/ubuntu bionic-security/main armhf Packages
Ign:21 http://archive.ubuntu.com/ubuntu bionic-updates/restricted armhf Packages
Ign:16 http://security.ubuntu.com/ubuntu bionic-security/universe armhf Packages
Ign:22 http://archive.ubuntu.com/ubuntu bionic-updates/universe armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu bionic-security/multiverse armhf Packages
Get:23 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [569 kB]
Err:14 http://security.ubuntu.com/ubuntu bionic-security/main armhf Packages
404 Not Found [IP: 91.189.88.149 80]
Ign:16 http://security.ubuntu.com/ubuntu bionic-security/universe armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu bionic-security/multiverse armhf Packages
Get:24 http://archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [151 kB]
Ign:25 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse armhf Packages
Ign:9 http://archive.ubuntu.com/ubuntu bionic/main armhf Packages
Ign:10 http://archive.ubuntu.com/ubuntu bionic/restricted armhf Packages
Ign:11 http://archive.ubuntu.com/ubuntu bionic/universe armhf Packages
Ign:12 http://archive.ubuntu.com/ubuntu bionic/multiverse armhf Packages
Ign:26 http://archive.ubuntu.com/ubuntu bionic-backports/universe armhf Packages
Ign:19 http://archive.ubuntu.com/ubuntu bionic-updates/main armhf Packages
Ign:21 http://archive.ubuntu.com/ubuntu bionic-updates/restricted armhf Packages
Ign:22 http://archive.ubuntu.com/ubuntu bionic-updates/universe armhf Packages
Ign:25 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse armhf Packages
Err:9 http://archive.ubuntu.com/ubuntu bionic/main armhf Packages
404 Not Found [IP: 91.189.88.161 80]
Ign:10 http://archive.ubuntu.com/ubuntu bionic/restricted armhf Packages
Ign:11 http://archive.ubuntu.com/ubuntu bionic/universe armhf Packages
Ign:12 http://archive.ubuntu.com/ubuntu bionic/multiverse armhf Packages
Ign:26 http://archive.ubuntu.com/ubuntu bionic-backports/universe armhf Packages
Ign:19 http://archive.ubuntu.com/ubuntu bionic-updates/main armhf Packages
Ign:21 http://archive.ubuntu.com/ubuntu bionic-updates/restricted armhf Packages
Ign:22 http://archive.ubuntu.com/ubuntu bionic-updates/universe armhf Packages
Ign:25 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse armhf Packages
Ign:26 http://archive.ubuntu.com/ubuntu bionic-backports/universe armhf Packages
Err:19 http://archive.ubuntu.com/ubuntu bionic-updates/main armhf Packages
404 Not Found [IP: 91.189.88.161 80]
Ign:21 http://archive.ubuntu.com/ubuntu bionic-updates/restricted armhf Packages
Ign:22 http://archive.ubuntu.com/ubuntu bionic-updates/universe armhf Packages
Ign:25 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse armhf Packages
Err:26 http://archive.ubuntu.com/ubuntu bionic-backports/universe armhf Packages
404 Not Found [IP: 91.189.88.161 80]
Fetched 1682 kB in 9s (181 kB/s)
Reading package lists... Done
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/main/binary-armhf/Packages 404 Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/binary-armhf/Packages 404 Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/main/binary-armhf/Packages 404 Not Found [IP: 91.189.88.149 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/universe/binary-armhf/Packages 404 Not Found [IP: 91.189.88.161 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
$ sudo apt install libssl-dev:armhf
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package libssl-dev:armhf
I do notice the errors about missing index files, but from looking at the launchpad page, libssl-dev is not in one of those indexes.
