Sorry for it, but we cannot provide support for undocumented Endpoints.
I highly recommend to not use it, as it being undocumented most likely means it is not meant for third party consumption and may be considered a breach of the developer agreement, which may come with legal action being taken.
Additionally, as you also mentioned, kraken is very End-Of-Life and will be shut down within the next month, so your time with it will be very limited.
What exactly is your usecase? Maybe there can be a different solution for what you’re aiming for!