Installing Quanteda version 2.1.2 I ran into issues and this is just a quick reference how it was fixed. I was using Ubuntu 18.04 and originally using R base of 3.4 but this was the first issue.
Updating R base, I was on 3.4 and updated to R 3.6.3. This got further in the package install but still was throwing errors.
ERROR: configuration failed for package ‘xml2’
Resolving this was installing libxml2-dev
ERROR: dependency ‘openssl’ is not available for package ‘httr’
Resolved by installing libssl-dev
After this, package installed successfully.