Lower minimum OTP to 27 and validate in CI

The OTP 28/29 support work was source-compatible with 27, so the
minimum_otp_vsn floor was raised further than needed. Set it back to 27
and add OTP 27 to the CI matrix (Python 3.12/3.13/3.14 on Linux) to
actually validate builds and the Common Test suite there.

Author: benoitc

.github/workflows/ci.yml

@@ -15,6 +15,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          # Linux - OTP 27 (minimum supported)
+          - os: ubuntu-24.04
+            otp: "27"
+            python: "3.12"
+          - os: ubuntu-24.04
+            otp: "27"
+            python: "3.13"
+          - os: ubuntu-24.04
+            otp: "27"
+            python: "3.14"
           # Linux - OTP 28
           - os: ubuntu-24.04
             otp: "28"
@@ -130,7 +140,7 @@ jobs:
           usesh: true
           prepare: |
             # Stock `erlang` pkg lags at OTP 26; use the versioned runtime
-            # package so we test on a supported OTP (28+).
+            # package so we test on a supported OTP (27+).
             pkg install -y erlang-runtime28 ${{ matrix.python_pkg }} cmake
             # numpy package follows the py<noDot>-numpy convention.
             # Non-fatal: not every FreeBSD pkg snapshot ships numpy for

CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## Unreleased
+
+### Changed
+
+- **Lower minimum OTP to 27** - `minimum_otp_vsn` is now `27`. The OTP 28/29
+  support work was source-compatible with 27 (the `try ... catch` cleanups build
+  fine there), so the floor was raised further than needed. CI now also builds and
+  runs the full Common Test suite on OTP 27 across Python 3.12/3.13/3.14.
+
 ## 3.1.0 (2026-05-30)
 
 ### Fixed

README.md

@@ -37,7 +37,7 @@ Key features:
 
 ## Requirements
 
-- Erlang/OTP 28+ (tested on OTP 28 and 29)
+- Erlang/OTP 27+ (tested on OTP 27, 28, and 29)
 - Python 3.12+ (3.13+ for free-threading)
 - C compiler (gcc, clang)
 

rebar.config

@@ -1,6 +1,6 @@
 {erl_opts, [debug_info]}.
 
-{minimum_otp_vsn, "28"}.
+{minimum_otp_vsn, "27"}.
 
 {xref_checks, [
     undefined_function_calls,