RSS feed 404

I made a mistake by posting this message twice, so a moderator closed it.
Really need some help with this problem, so I try again:

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/ error 404
I tried all weekend to fix the problem,and I still have no clue.
Someone to help?
And also I use Cloudflare and Category Specific RSS Menu
The template is not an issue, I tried with Twenty Sixteen and Twenty Seventeen with the same result: error 404
I also deactivate all plungins, and restored WordPress files with no results.
Thanks for any idea to fix the issue
The site food styling