This comes up on occasion, like Time stamp validation, missing certificate on Stack Overflow. In the SO question, the developer is tring to get his data signed by a commercial CA that offers a “free” time stamping service.
Later, after trouble shooting the disconnect between the marketing literature and the operational failures, the developer commented:
I am now under the impression that they’re not really free. I think it’s a free “add on” to some other products they sell, perhaps.
I’ve also needed a time stamp service a few times in the past. The occassions are infrequent, but when they are needed, its usually a pain point.
Please consider adding a free Timestamp service to the Let’s Encrypt offerings.