Subdomains lacking IPv6 connectivity

[86dd]

Hello,
I was looking at makedeb and noticed that it only fetches over IPv4, despite being on a dual-stacked system.
I have done some digging and noticed that the following subdomains lack IPv6:
shlink.makedeb.org, proget.makedeb.org, mpr.makedeb.org, minecraft.makedeb.org
They all seem to be a CNAME to proxy.hunterwittenborn.com however, so one AAAA record and maybe some configuring of the host should do the job.
The IPv4 is registerred to Linode, which to my knowledge does support IPv6 and should usually be auto-configured.
I have found a documentation on compute instances here: https://techdocs.akamai.com/cloud-computing/docs/an-overview-of-ipv6-on-linode
I hope this helps.