It has occurred to me that this can be accomplished using just
https://api.blockchair.com/bitcoin/transactions?s=time(desc) but it will limit you to 10 results at a time ( insert &offset=10 or 20 or 30 etc. into the query to get the next recent records).
Also, since there can be several hundred transactions in a block, none of them having a timestamp, it becomes ambiguous what the most recent 100 transactions are within a block.
For example, blockchair API have a limit of 1440 requests per day for free
It's actually 1000 requests per day.