module Roda::RodaPlugins::MultibyteStringMatcher::RequestMethods

def _match_string(str)

approach as in Roda 3.0.
Use multibyte safe string matcher, using the same
def _match_string(str)
  rp = @remaining_path
  if rp.start_with?("/#{str}")
    last = str.length + 1
    case rp[last]
    when "/"
      @remaining_path = rp[last, rp.length]
    when nil
      @remaining_path = ""
    end
  end
end