Currently, release versions of PuTTY tools only run on Windows systems and Unix. The Windows version is provided in the form of executables, for both x86 and Arm based Windows systems. The Unix version is provided as source code (although at least some Linux distributions provide it pre-built).
Our standard Windows executable builds aim to run on all versions of Windows still in security support. Earlier versions might be supported if it's easy, but we don't promise to test them reliably. (For example, PuTTY 0.83 still runs on Windows XP – but the previous release 0.82 didn't.)
We do not have release-quality ports for any other systems at the present time. If anyone told you we had an Android port, or an iOS port, or any other port of PuTTY, they were mistaken. We don't.
There are some third-party ports to various platforms, mentioned on the Links page of our website.