I wouldn't dream of doing this on a live site. I'm exploring the mini-migration from Joomla3 to Joomla4 using a cloned copy of my live site, running in a test environment on my standalone desktop under XAMPP. That way, if I hit a brick wall with compatibility issues I can just delete the test site, reschedule the testing until after the issues are resolved and start again.
Thank you for letting me know I can ignore the incompatibility flags with regard to CB.