I used to have the following handy script to launch a new (fresh!) instance of Google Chrome when working on Chrome for Testing in the Browser Automation team at Google:

# start chrome with ephemeral settings (every run of Chrome is empty)
# usage: chrome-fresh out/Default/chrome

TMPDIR="$(mktemp -d)"
trap 'rm -rf "${TMPDIR}"' EXIT

CHROME="${1:-google-chrome}"; shift

# https://github.com/GoogleChrome/chrome-launcher/blob/main/docs/chrome-flags-for-tools.md

if [[ "$(uname -s)" == "Darwin" && "$CHROME" == *.app ]]; then
	open -n "$CHROME" --args "$CHROME_FLAGS" --user-data-dir="$TMPDIR" "$@"
else  # "Linux"
	"$CHROME" "$CHROME_FLAGS" --user-data-dir="$TMPDIR" "$@"

The script is self-documenting, it was properly tested on both Linux and macOS.

The typical use case would be to compile a new Google Chrome binary (/out/Default/chrome), and then use the script to launch it with a fresh user data directory, to ensure the previous launch settings do not interfere with the current one.