The messages [[ https://gerrit.wikimedia.org/g/mediawiki/extensions/WikimediaMessages/+/5bf955e0aeb811de8155057a7994c45ebc0ed505/i18n/wikimedia/en.json#264 | wikimedia-mobile-terms ]] contains link to https://m.foundation.wikimedia.org/wiki/Terms_of_Use which does not work. I could not find the message used anywhere in the interface, so maybe the code at https://codesearch.wmflabs.org/search/?q=getTermsLink&i=nope&files=&repos= is broken.
The message that is used is mobile-frontend-terms-url . This is set for certain projects, but not all projects as some projects e.g. mediawiki.org do not set the message.
It's unclear whether this is up to the projects to update or whether there should be a generic catch all message in WikimediaMessages. if the former we should delete it. If the latter we should rename.
= Proposed fix
[] rename the message key wikimedia-mobile-terms in WikimediaMessages to mobile-frontend-terms-url
[] Update value to https://foundation.wikimedia.org/wiki/Terms_of_Use