As a prelude to IPv6 support on Cloudron itself, we have added IPv6 support to the Appstore now. https://cloudron.io should now work over IPv6. If anyone hits any connectivity issue, please let us know here.
@mehdi indeed. That is the case on many residential ISPs at least in Germany. The only working solution here is to request a real ipv4 from the ISP, which usually is possible, but likely will cost extra in the foreseeable future.