PSA recently gained interruptible functions for signing and verifying hash-based signatures. So far, these functions are not used by X.509 or TLS, but they should be used when MBEDTLS_USE_PSA_CRYPTO enabled, in all places that currently support restartable operations using the legacy API (that's currently just 1.2 with the ECDHE-ECDSA key exchange, including client authentication), in order to avoid feature gaps in PSA-based builds.