I'd like to offer a solution. Don't use Gmail. LOL, J/K! (dont you love when people give you "solutions" like that?)
I struggled with this for about 2 days. Seems outlook wants a folder CALLED Archive, which in the past you could have created and would be honored. Gmail has somewhat recently integrated an alias for Archive into its AllMail folder. I was able to get this working by simply going into gmail, and under the label management, finding the AllMail item, which is by default hidden, and telling it to show it in gmail, as well as checking show in imap. As soon as I made that change and triggered a sync in outlook mobile, archiving works. The same is true for windows 10 mail on the desktop now. Give it a try and report back if it was successful! I'm only able to test on my own single account, so I can't say its a definite solution yet for sure, but the research and preliminary results seem to suggest this should work for everyone.