If I remember correctly, your web browser must support “ReplaceAll” in order to work with the latest version of Discourse. If it doesn’t, you’ll have to browse Discourse using the basic HTML view.
Support for “ReplaceAll” was added to version 85 of Google Chrome (released on August 24, 2020), so it’s likely that your Chromebook reached end-of-life at an earlier point in the year.
You should definitely do that. Newer Chromebooks are supported for nearly a decade.