> "a reasonable touring bike if done within its constraints"

Yes; for example, YouTuber Susanna Thornton does bikepacking and wild-camping on her Brompton: https://www.youtube.com/@susannathornton/videos

and Darin's Adventure Chronicles: https://www.youtube.com/@darinsadventurechronicles/videos

Many other one-off videos exist too under searches for brompton bikepacking and brompton wildcamp.