TL;DR: your CPU is too old for the default polars build. Install polars-lts-cpu, which is compiled for older instruction sets.

## The error
```text
Illegal instruction (core dumped)
```

## Fix it
1. Remove the default build:
   ```
   pip uninstall -y polars
   ```
2. Install the long-term-support CPU build:
   ```
   pip install polars-lts-cpu
   ```
   Expected: install completes.
3. Verify:
   ```
   python -c "import polars; print(polars.__version__)"
   ```
   Expected: imports cleanly, no crash.

## When this applies
Use this when `import polars` crashes the interpreter with illegal instruction on old hardware, VMs masking CPU features, or under emulation.

## When it does not apply
If the crash happens on a modern CPU, the install is corrupt; reinstall plain polars. If a different library crashes, this fix does not apply.

## Compatibility
polars-lts-cpu tracks polars releases with an older-CPU build. The API is identical; only the compiled code differs.

## Root cause
Default polars wheels use modern SIMD instructions for speed. CPUs without those features trap the illegal instruction the moment the native module loads, killing the process before any Python error can surface.

## Edge cases
Do not install both polars and polars-lts-cpu in one env; they conflict. Cloud VMs sometimes hide CPU flags; if the LTS build still crashes, the vCPU truly lacks the features and the LTS build is the only option.