You want to try something interesting but want to dual-boot. That last bit could be difficult or “impossible” but using a VM or running from USB stick are options.
www.haiku-os.org I’ve run it from USB stick on some older laptop.
www.gobolinux.org GoboLinux is an alternative Linux distribution which redefines the entire filesystem hierarchy. Doesn’t seem up to date but quite interesting. If I remember well you can have different versions of software installed at the same time. Let’s say (making this up) Bash 1.1, 3.1 and 5.2
bedrocklinux.org Bedrock Linux is a meta Linux distribution which allows users to mix-and-match components from other, typically incompatible distributions.