Lattice ICE 40
Lattice ICE 40 was the initial FPGA supported by the open source Yosys synthesis suite.
ICE 40 is an older slower smaller and less expensive family of FPGAs. Great for educational projects, and simple applications. They are limited to 8K LUTs, and 100 Mhz. Most have small memories, the UP5K also has 1 Mbit of Large RAMs, but they are single port memories, and limited to 50Mhz.
The Pico-Ice and Pico2-Ice are recommended for beginners. Both use the wondrerful Pico Ice SDK. The Upduino 3.1 fixed the bugs of the previous versions, but retained the internal, less accurate oscilator as the default. And only 1 of 4 pins of the FTDI FT232H USB bridge are connected to the FPGA. At least they can be manually connected.
There are many open source circuit boards using Lattice FPGAs, but sadly most are not shipping.