If anyone's interested in getting into FPGA stuff, the iCE40UP5K (the 5K indicates the number of LUTs; there are other sizes available) has an open-source toolchain that works very well. There are pretty cheap development boards using this FPGA, I use the UPduino, which I bought in 2019 or so. (Recently the same team released a new UPduino dev board that also includes an RP2040, which is probably pretty useful, available at https://lectronz.com/products/pico-ice-rp2040-plus-lattice-i...)
What can you do with an FPGA of this size? Not too much, but it's about enough to, for example, fit an implementation of a YM2151 FM audio chip (audio chip from the 80s that was used in synthesizers and arcade machines). I think it would probably also be big enough for old CPUs such as the Z80 or 6502. Unfortunately it's not 5V-tolerant so you can't wire it directly to parts of that era.
I second the upduino, it's a great board. Recently i have been using the iCESugar-pro which is also supported by the open source toolchain, and comes in a handy SODIMM form factor that makes it easy to incorporate into real projects. It uses the lattice LFE5U-25F-6BG256C with 24k LUTs and 32 MB SDRAM, 106 usable i/o connections, about $60.
What can you do with an FPGA of this size? Not too much, but it's about enough to, for example, fit an implementation of a YM2151 FM audio chip (audio chip from the 80s that was used in synthesizers and arcade machines). I think it would probably also be big enough for old CPUs such as the Z80 or 6502. Unfortunately it's not 5V-tolerant so you can't wire it directly to parts of that era.