Hi @bambuino . It's USBHostMSD (not to be confused with USBMSD).
I'm using my M4s as dataloggers without issue (now that I've found USB flash drives that work Unreliable file writing on connected flash drive - #15 by steve9.._gaMjI1MDUyOTkzLjE3MzYwNjAwMzY._ga_NEXN8H46L5MTczNjA2MDAzNS4xLjAuMTczNjA2MDAzNS4wLjAuNzE5NDg2Njg4)
You'll need commit STM32H747: core_m4: fix compatibility with core 4.0.10+ · arduino-libraries/Arduino_USBHostMbed5@782ede3 · GitHub
which was applied after the last release. Download from git rather than use the IDE library manager.
The chrono messages are just deprecation warnings that can be ignored, delay works fine.