Is it permissible to greet with 'peace' in a language other than Arabic – such as Albanian – to include non-Muslims, or does Islam command greeting with 'peace' in the Arabic language?

Giving greetings (Salam) is permissible in Arabic and other languages. There is no need to object to someone who gives greetings in a language other than Arabic, for the matter is broad. It may even be preferable to give greetings in a non-Arabic language if there is a benefit in doing so. The preponderant view is that giving greetings in a non-Arabic language (al-ajamiyyah) is valid, and responding to it is obligatory if the addressee understands it, because it is considered a greeting and an act of peace. This applies to greetings outside of prayer. If giving greetings in a non-Arabic language fosters affection and prevents aversion, then it might be better. Indeed, the Prophet, peace and blessings be upon him, gave greetings to an assembly that included a mixture of Muslims, polytheists, and Jews.