As shown in the screenshot below, the language setting of the forums on my end changed to a random language (can’t guess what it is). I had it on Auto, so I managed to navigate to the page to change it to English, manually.
Running MacOS 10.13 Public Beta (build 17a315)
Latest version of Safari from Mac App Store (not beta)
Also occurred on my iPhone 7 Plus running iOS11 Public Beta
Occurs both when accessing through the latest version of Chrome and Safari.
Both devices had the same language, despite being on “Auto”
Maybe something for the discourse team to look into?