If I recall correctly, in Webflow’s hosting redirects, you can enter external URLs as the destination.
So, e.g. /about could go to https://somesite.com/about.
Try it, I’m pretty sure that worked last time I was playing with redirects… because it surprised me.
Remember, of course, if you have an /about page on your site, it will then be inaccessible with a redirect in place. But that might be the point.