@tkimnguyen On current Volto sites you should be able to change the logo via the controlpanel: https://demo.plone.org/controlpanel/site. Though to me it seems a bit bugged.
Thanks @jackahl – I had been trying it on a site I'm working on that is a clone of the 2024 conference site, but it didn't seem to work. Now I see that you have to change the logo (to, say, image Y) and save the change, then change the logo AGAIN (to image Z) and save, and when you reload the home page you see that the logo has changed... to image Y 