Rss feed 404

I have a site using Polylang for 3 languages. I publish my feeds with Feedburner, each language with a distinct url.
The French url works well, the Dutch and English publish the French comments.
When I try to go to https://domain.tld/?feed=rss2 I get a 404 error (not found), and a redirection to /feed/.
I tried all weekend to fix the problem,and I still have no clue.
Someone to help?
And also I use Cloudflare, Category Specific RSS Menu
The template is not an issue, I tried with Twenty Sixteen and Twenty Seventeen with the same result:404
Thanks for any idea to fix the issue