Raspberry Pi Pico Bit-Bangs 100 Mbit/S Ethernet

I wish something like Pi Pico existed but with 1GHz clock, DDR3 memory interface and PCIe and few dozens of GPIO.

Xilinx Zync have PL for FPGA programmable logic, and PS with a few different ARM cores. They aren't as cheap as a Pi Pico though.

A RPi 4/5 has that? The OMAP 3/4 chips in Beaglebone is another alternative. Or Rockchip/Allwinner SoCs. Those are all Cortex A series though, but that can still be programmed bare metal if one wants. There are also Cortex M microcontrollers with support for SDRAM, like STM32H7. Or one can get an FPGA with DDR support like ECP5.