> Non-portable scripts can also bite you on Linux, where Debian, for example, will swap out the shell from bash to dash for performance. but others will not. So, even within the Linux ecosystem, you can end up with scripts that behave differently across distros.

From the bash man page, "If bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well." Also you should not be including bashisms if your shebang is sh and not bash. So using bash as sh shouldn't generally be a problem, if you stick to the published Shell Command Language [0], unless you hit one of the cases where the spec is a bit ambiguous and shells implement it differently [1].

[0] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V... [1] https://stackoverflow.com/questions/16069339/different-pipel...