I have had to build and support large multi-language sites for large clients where SEO was critical. Since the requirements typically included multi-language at the beginning I used a CMF / CMS that has this functionality in the core. For clients that decided to do it later, I migrated them. If there is a bunch of money on the table (potential international business) then you might consider the same.
There is a tutorial you could look at that is a workaround. [TUTORIAL] Full Multi Language Site - Easy to set-up and to use!
You can hack a webflow site to accomplish the content side (partial) but not the SEO. Until the features exist in the core, I suggest looking at an alternate.
My choice for multi-language sites is processwire.com . When you enable a the feature ,
fields are created for each language in a template. You populate the content, use the same images and code, and the engine will render the language in a subdirectory matching the language abbreviation. All meta-tags are set to each language. There are other solutions as well. I like PW because there are no limits and I can theme it with a design created in webflow rather easily.
Got a budget? Feel free to PM me.