Defining a stable API to code against?
> And with many things being Linux (or Linux-like like WSL) the need for this might be less?
Define "being Linux". RHEL? Ubuntu? Other? Is /bin/sh linked to Bash or something?
* https://mywiki.wooledge.org/Bashism
* https://linux.die.net/man/1/checkbashisms
> Are Android and/or iOS fully POSIX compliant?
UNIX® Certified Products include macOS:
* https://www.opengroup.org/openbrand/register/
POSIX:
* https://posix.opengroup.org/register.html