When I need to use Chrome, I just use the Chrome Mask extension in Firefox to change my user agent. I haven’t had a site that actually failed to work on the Gecko engine instead of Chromium. It’s just lazy devs checking your user agent to see if you’re using Chromium, and then throwing a fit if you’re not.

Chrome Mask even has a built in site reporter, because broken sites don’t actually conform to modern web interoperability requirements. If it fails to work on Gecko, there’s a good chance that it will also fail to work on other platforms (like Apple’s WebKit) as well. And the reports go to the team that develops Firefox, so they can figure out why the site is refusing to work on Gecko.