Have never used free dyndns services myself. But if I would have to choose one right now I would give ipv64.net a try. Dennis has some excellent (german) YT tutorials and constantly improves his services.

I recently purchased three Lenovo m910q, which are now running as low-power proxmox cluster at my home for a very decent price. Here’s the shop: http://www.manotebooks.de/ Quite happy with it.