The main trick, not explained in the Cloudflare documentation, is that Cloudflare, by default, seems to send the ndjson as text/plain. On the Dynatrace side, this is interpreted as a single log line, instead of being considered as JSON data. That's why in the above example, there is an additional header field passed as "header_content-type=application/json", so that Cloudflare sends an appropriate Content-type header to Dynatrace.
After the configuration above, you should start seeing your Cloudflare logs flowing into Dynatrace
Other information can be configured to be pushed to Dynatrace. For more information on the Cloudflare side, check the Cloudflare Docs.