The Gowin chips are quite interesting - they have RAM built in to the FPGA itself. It's SDRAM in the case of the Tang Nano 20k. It's a 32-bit wide RAM, but unfortunately only 8 megabytes, which is a bit limiting. The FPGA's clocking is a bit limited, too.
(For that reason, there's an extra clock generator on the Tang Nano 20k.)
