What is the best alternative to a-Shell on iPhone?

Termiux, A tier, #2 in terminal emulation.

Is there a free alternative to a-Shell?

Yes: Termiux (A tier, #2) is free to download, with in-app purchases.

No. a-Shell is #1 in terminal emulation.

a-Shell is S tier, #1 of the 7 tiered apps in terminal emulation. Here is everything that competes with it on iPhone, in tier order.

2
TermiuxA
Free + IAP · ★ 4.4 · 68 ratings · score 84
Terminal app for iPhone with a built-in command-line environment, extended keyboard, and SSH and SFTP access to your.
3
iSH ShellC
Free download · ★ 4.7 · 5,201 ratings · score 68
A Linux-like shell for iOS where you can edit files with sed and cat, and move them around.
4
a-Shell miniC
Free download · ★ 4.3 · 666 ratings · score 62
Local terminal emulator for iOS that runs most Unix commands, including vim, Python, git and ffmpeg.
5
ViSH - AI Coding TerminalF
Free + IAP · ★ 3.0 · 2 ratings · score 46
Runs a local ARM64 Linux environment (Alpine or Ubuntu 24.04) in a touch terminal on iPad, with file browsing and SSH.
6
Terminal Emulator appF
Free download · ★ 1.9 · 9 ratings · score 16
A web-based terminal emulator for running quick functions such as common unit conversions and quick math.
7
Terminal Emulator PlusF
Free download · ★ 1.0 · 2 ratings · score 12
Free Utilities app that gives access to different types of shell, with a web front-end for quick conversions and math.

What is the best alternative to a-Shell on iPhone?: Termiux, A tier, #2 in terminal emulation.
Is there a free alternative to a-Shell?: Yes: Termiux (A tier, #2) is free to download, with in-app purchases.
Does anything rank above a-Shell?: No. a-Shell is #1 in terminal emulation.