Language packs are not available for download from the Moodle interface itself or during the installation of a site.

Unable to connect to the download server. It is not possible to install or update the language packs automatically. Please download the appropriate ZIP file(s) from https://download.moodle.org/langpack/3.10/ and unzip them manually to your data directory

1. curl -I --http1.1 https://download.moodle.org/langpack/3.10/languages.md5
   HTTP/1.1 503 Service Temporarily Unavailable
   Date: Sun, 31 Jan 2021 09:45:41 GMT
   Content-Type: text/html; charset=UTF-8
   Connection: close
   X-Frame-Options: SAMEORIGIN
   Set-Cookie: __cfduid=d0cf3177fff32b42a564c8413dfd3abe01612086341; expires=Tue, 02-Mar-21 09:45:41 GMT; path=/; domain=.moodle.org; HttpOnly; SameSite=Lax
   Cache-Control: private, max-age=0, no-store, no-cache, must-revalidate, post-check=0, pre-check=0
   Expires: Thu, 01 Jan 1970 00:00:01 GMT
   cf-request-id: 07f96e88da000030e6c4332000000001
   Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
   Server: cloudflare
   CF-RAY: 61a280548f5230e6-ORD

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