Continuing the discussion from Interfacing modern MCU's to older hardware:
I was reminded of @RichardP’s thread when I saw this series of articles:
This fellow has put a BeagleBone Black on the UNIBUS of a PDP-11 as a standard peripheral device, and can emulate a variety of peripherals using the Linux machine. The PRUs (small, RISC embedded processors) attached to the GPIOs on the BBB enable him to get around some of the timing problems that @RichardP is experiencing putting an ESP32 on an Amiga memory bus.
The project is very interesting and very well documented, and includes a little bit of everything. The custom board, of course, but also some custom 3D-printed parts to keep the profile low enough to fit in a standard UNIBUS slot, as well as software to emulate UNIBUS memory expansion cards and hard disk controllers with attached hard disks – it even goes so far as to include a 3D printed case that mounts the original HDD lamps and buttons from the HDD device!
It looks like the project came about some time last year, and is still under active development; there is a Google Group with a number of messages this month.