Get a usb drive and try out different distros before committing. With Linux you can make use of a feature called LiveUSB which allows you to boot from USB a full usable operating system without changing anything in your filesystem.
The steps here should work for any distro not just Ubuntu. https://documentation.ubuntu.com/desktop/en/latest/how-to/create-a-bootable-usb-stick/
Once created, restart your mac and hold alt when you hear the chime and select the USB drive from the boot screen. Spend sometime in the new OS, get a feel for it, and if you like it you can install, if not, restart and you will be back in macOS as if nothing happened.