This is a notice that the snap tpm2 is going to be deprecated. The TPM resource manager (RM) shipped as part of this snap is no longer supported. Also due to the original design of the snap, it’s not easy to use the tools and/or libraries it contains to deploy a TPM application in another snap. Ideally anyone developing a tpm-based application should include the tpm2-tss and tpm2-tools debian packages using snapcraft’s stage-packages mechanism. A userspace RM manager is also no longer required in Ubuntu 18.04 LTS (or Ubuntu Core 18) or later, as the kernel-provided RM can be used.
Note - the in-kernel TPM RM was added as of the 4.11 kernel, so in order to use the TPM on classic 16.04 or Ubuntu Core 16, a userspace RM is still required. A replacement exists called abrmd, however as a debian package is not available for 16.04 from the archive, it would need to be built from source code:
https://github.com/tpm2-software/tpm2-abrmd
The source code of the tpm2 snap is available here:
https://code.launchpad.net/~snappy-hwe-team/snappy-hwe-snaps/+git/tpm2