request from https to http

I have my domain in Cloudflare which I use as DNS.
From my website I want to make requests to a local server running on a raspberry through the IP.
I get an error because the website is https and the raspberry is http.
If I generate an auto-generated ssl, would it work or would I have to create an ssl with a CA like Let's encrypt?
If I do it with let's encrypt, do I have to do something in cloudflare so that the raspberry domain is ip.mydomain.com?
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