@saphirata if your IP of your ISP connection (local ip) keeps changing, then you need to keep the DNS records in-sync. So for your use-case it means you have to keep adjusting the settings in Cloudflare.
Maybe for a start you could disable Cloudflare proxying and use it normally as a DNS service, then configuring your domain in Cloudron to use our Cloudflare backend and enable https://docs.cloudron.io/networking/#dynamic-dns