How can I message a friend on Lernu? I can see their profile but I can see no option to message them.

unfortunately lernu.net closed this function some years ago (maybe the team shrinked and cannot control the page enough).

So you have these oportunities to contact people.

Write a public message like yours and write there your email-adress o.s.

Write the email-adress into your profile.

Ask the person you want to contact in your "friends"-list to accept your application,
and then write your email-adress to your "friends"