Biscuit recognizes Tails and Whonix by itself. On both, it uses the system’s Tor instead of starting its own, and every connection goes through it, atomic swaps included.
chmod +x biscuit-*.AppImage.Biscuit keeps its wallets and settings in a biscuit_data folder next to the AppImage, so they survive a restart. Don’t install a .deb with apt on Tails: it would be gone at the next start.
Tails needs glibc 2.34 for atomic swaps: Tails 6 and later have it.
Run Biscuit in the Whonix Workstation, from the AppImage or the .deb. Biscuit uses the Workstation’s Tor through the Gateway, and doesn’t start a Tor of its own.
Exchange swaps can’t be created through Tor (see why), so they’re off on Tails and Whonix. Atomic swaps work.