Building Better Environments for Autonomous Cyber Defence. - Chris Hicks; Elizabeth Bates; Shae McFadden; Isaac Symes Thompson; Myles Foley; Ed Chapman; Nickolas Espinosa Dice; Ankita Samaddar; Joshua Sylvester; Himanshu Neema; Nicholas Butts; Nate Foster; et al. (CoRR, 2026)