Mattermost for Roundcube

[ru_matrix]

Does anyone have a mattermost version of Windows for instructions:
Find the file /mattermost/mattermost/web/templates/head.html
Comment out the security feature by changing <style id = "antiClickjack"> body {display: none! Important;} </style> to <! - <style id = "antiClickjack"> body {display: none! Important;} </style> ->

or step-by-step instructions for embedding mattermost in Roundcube...