UART is the simplest board-visible debug channel, but it still needs clock-derived baud timing, synchronizers and a testbench.
A UART echo is a good second project after blink. It forces clock math, serial timing, RX synchronization and a repeatable board-visible result.
Compact Gowin GW2AR board with HDMI, audio amplifier, TF card slot, SDRAM, and onboard debugger.
Gowin Semiconductor GW2AR20,736 LUTopen toolchain28.17 USD
Open-source educational Lattice iCE40UP5K board designed around the Yosys, nextpnr and IceStorm flow.
Lattice Semiconductor iCE40 UltraPlus5,280 LUTopen toolchainprice at the seller
Digilent Artix-7 board with Vivado WebPACK support, Pmods, Arduino/chipKIT style expansion, DDR3 and Ethernet.
AMD/Xilinx Artix-7open toolchainprice at the seller
