Usually, claiming a domain should not take longer than some minutes or a some hours at max.
Maybe it´s worth to retry again. If that does not work I would suggest to connect with Pinterest Support Teams, as we have no influence on their processes.
Currently we do not offer a Pinterest Catalog Feed, but it is in our idea backlog.
Claiming a domain through the offered solutions is currently not supported in standalone shops. You might consider to embed your shop into a hosted website and to use one of the prefered methods.
We will put this on our idea list to support you guys with such a feature in the future.
We´ve double checked again with the information that Pinterest is sharing.
Unfortunately, this is just not possible, because Pinterest claiming is done per domain .
This is different from Google, which allows claiming per url path .
Because all (say german) standalone shops run on shop.spreadshirt.de, multiple independent shop owners can not claim the same domain.
The only remaining option is to run an integrated shop. There, partners can follow the usual claiming process using the tag.