korn shell (ksh)
ksh is known for its faster execution of scripts, so I downloaded
Portable OpenBSD ksh. Not an official OpenBSD project.
Unlike other ports of OpenBSD ksh, this port is entirely self-contained and aims to be maximally portable across operating systems and C compilers.
./configure;make;make install
that, created a sym link ln -s /usr/local/bin/oksh /bin/ksh
and changed /etc/passwd for root to use /bin/ksh as its shell instead of /bin/sh (that links to bash)
Rebooted and perhaps psychologically but it does seem the system runs much quicker in general
If you're entrusting enough the executable is attached (actually gzip'd, around 256K non-compressed), although loading the devx and grabbing/compiling the source is dead easy.
Similar but different syntax to bash. https://www.educba.com/korn-shell-vs-bash/
There may (will) be some conflicts i.e. some scripts where syntax differences will cause errors, So very experimental, only use in a read-only session or as a standalone rather than a replacement.