docs: document arm64 -generic variant for non-AWS ARM hosts

The default aarch64-linux-0.10.0 binary is AWS Graviton-tuned and
SIGILLs on Ampere Altra / Oracle Ampere / Apple Silicon (under a Linux
Docker container). Built a second portable ARMv8-a variant (tagged
-generic / aarch64-generic-linux-0.10.0) and published it alongside:

- s3://boilstream.com/binaries/linux-aarch64/boilstream{,-admin}-0.10.0-generic
- boilinginsights/boilstream:aarch64-generic-linux-0.10.0

README now lists both paths and calls out which to pick. CHANGELOG
notes the variant.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dforsber

CHANGELOG.md

@@ -45,6 +45,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Helm chart de-localized**: Example charts no longer embed localhost certificates or hard-coded dev hostnames — production deploys use real FQDNs end-to-end
 - **boilstream-admin wrapper for K8s**: New `scripts/boilstream-admin-k8s.sh` reads CA, superadmin password, and MFA secret live from Kubernetes `Secret`s; computes TOTP locally and execs the admin CLI against the in-cluster deployment
 - **`testMode.disableTurnstile` chart value**: Lets CI/test clusters skip the Turnstile CAPTCHA on `/auth/email/signup` without rebuilding the image
+- **Portable ARM64 Linux variant (`-generic` / `aarch64-generic-linux-0.10.0`)**: The default `aarch64-linux-0.10.0` build is AWS Graviton-tuned and uses extensions not present on Ampere Altra / Oracle Ampere / Apple Silicon (when run in a Linux Docker container); the new `-generic` variant is built against the ARMv8-a baseline so it runs everywhere. Both are published side-by-side on S3 and Docker Hub.
 
 ## [0.9.0] - 2026-04-08
 

README.md

@@ -38,19 +38,31 @@ See [GitHub releases](https://github.com/boilingdata/boilstream/releases) for th
 
 ```bash
 # Download — pick your platform from:
-#   darwin-aarch64 (Apple Silicon), darwin-x64 (Intel Mac),
-#   linux-aarch64 (Linux ARM64), linux-x64 (Linux x86_64), windows-x64 (Windows)
+#   darwin-aarch64   Apple Silicon Mac
+#   darwin-x64       Intel Mac
+#   linux-aarch64    Linux ARM64 — AWS Graviton-tuned (fastest on AWS EC2 Graviton 2/3/4)
+#   linux-x64        Linux x86_64
+#   windows-x64      Windows
 # Replace {VERSION} with the latest release (see GitHub releases above, e.g. 0.10.0)
 curl -L -o boilstream https://www.boilstream.com/binaries/darwin-aarch64/boilstream-{VERSION}
 curl -L -o boilstream-admin https://www.boilstream.com/binaries/darwin-aarch64/boilstream-admin-{VERSION}
 chmod +x boilstream boilstream-admin
 
+# Non-AWS ARM64 (Hetzner, Oracle Ampere, Apple Silicon inside a Linux Docker container):
+# the default linux-aarch64 build uses AWS Graviton extensions and will SIGILL on
+# Ampere Altra and similar. Use the -generic variant instead:
+#   curl -L -o boilstream       https://www.boilstream.com/binaries/linux-aarch64/boilstream-{VERSION}-generic
+#   curl -L -o boilstream-admin https://www.boilstream.com/binaries/linux-aarch64/boilstream-admin-{VERSION}-generic
+
 SERVER_IP_ADDRESS=1.2.3.4 ./boilstream
 
-# Docker
+# Docker — AWS Graviton or x86_64:
 docker run -v ./config.yaml:/app/config.yaml \
    -p 443:443 -p 5432:5432 -p 50051:50051 -p 50250:50250 \
    -e SERVER_IP_ADDRESS=1.2.3.4 boilinginsights/boilstream:aarch64-linux-{VERSION}
+
+# Docker on non-AWS ARM64 (Hetzner, Oracle Ampere, Apple Silicon):
+#   boilinginsights/boilstream:aarch64-generic-linux-{VERSION}
 ```
 
 > _Use the accompanying `docker-compose.yml` to start Grafana and MinIO_