Seeing a lot of articles mentioning the use of DMA to set up the TLAST signal, I use HLS to create the IP cores, connect in vivado. Where and where should the TLAST signal be set in which software?
I would suggest you familiarize yourself with the AXI4 standard and in particular the stream version.
There are a few post in the forum that deals with this, for instance:
Code example here: https://github.com/Xilinx/Vitis-HLS-Introductory-Examples/tree/master/Interface/Streaming