Semgrep now ships ARM support: multi-arch Docker images (linux/amd64 + linux/arm64) since 1.31.2, aarch64 Python wheels on PyPI since 1.33.1, and musllinux (Alpine) aarch64 wheels since 1.38.0. Upgrade to 1.38.0 or later on ARM, for Docker use the multi-arch image, for pip install grab a current wheel.
Source: https://github.com/semgrep/semgrep/issues/2252
Source: https://github.com/semgrep/semgrep/issues/2252