The Arm® Ethos-N support in TVM is based on the Arm Ethos-N driver stack (GitHub - ARM-software/ethos-n-driver-stack: Driver stack (including user space libraries, kernel module and firmware) for the Arm® Ethos™-N NPU).
The Ethos-N driver stack team has announced in the recent 21.05 release notes that support for Ethos-N77 will be deprecated in favour of Ethos-N78 and will be removed in their 21.08 release, due at the end of August 2021. Support for the Ethos-N78 is already available in the TVM stack and is expanded to more configurations ([ETHOSN] Add support for non-default ethos-n78 configurations by tristan-arm · Pull Request #8300 · apache/tvm · GitHub). The Ethos-N78 configuration with 4 TOPS and 4 PLEs can replace the Ethos-N77 configuration.
Please contact us if this is an issue for you.