To address your 2nd point: as far as I know, Digital Ocean's IPv6 doesn't provide the things you'd need to run an IPv6-only server (e.g. there is no NAT64 or DNS64 gateway, no v4-to-v6 proxy for letting the v4 Internet reach your server).
And sure, if you just want a little bit of computing power and literally don't care where from, you might as well get a VM from somewhere like Digital Ocean instead of a Pi from Mythic Beasts, but that is beside the point. This is an offer to rent a Pi on an IPv6-only network, which nobody else is doing.