To add a few more options, MIDI Translator Pro can be great for prototyping “in the box” and can be used on their standalone Bome Box MIDI Translator Pro | Bome Software
Also, custom firmware can be written for the MkI Launchpad Pro
Just to unhelpfully increase your option paralysis…
All I really need is a simple, two-button controller that will send a fixed CC message with a value of 127 on every press of either button, so I can use it for punching in and out live on my old MPC (one button for replace, one for overdub) but whenever I go lookign for something the prices start around double what the cost of parts for a Pedalino would cost (and I already have an old Arduino Duo that’s been sitting around for years, so that makes it even cheaper).What I’m thinking about is making a sort of brain with the arduino, display, and maybe a couple knobs and buttons, and then put some 1/4" connectors on that for using any off the shelf expression pedals and footswitches, and probably a DB25 connector in case I want to make something bigger and connect it with an old printer cable. Eventually I could swap in a more powerful Arduino if I felt like I needed it.
Plus since it can do RTP I could finally build the ethernet board for my MIDIbox Seq and hopefully use one of its RTP ports to rout the second pair of MIDI ports from the MPC to the Seq and free up some ports and channels that I’m using to connect it with DIN MIDI right now.
For something that simple, I’d look for the Raspberry Pi Pico:
I looked at that but it’s just simple buttons, no MIDI processing, no continuous controllers as far as I could see, no OSC, no RTP-MIDI, and it would cost more because I don’t have any of the parts on hand.
Teensys support usb midi and din midi. Hooking up a few switches and pots is one of the simplest things you could do with it 
MIDI CC is supported (not that it makes much difference either way, based on your expanded requirements).
Oh cool, I didn’t notice that.
Ah sorry I just thought you needed two buttons. Knobs won’t work on the Pico Pi, indeed.
As mentioned by others, practically any Teensy will do you right - the Teensy LC is probably the cheapest and simplest solution.
No worries. That’s what I was looking for initially, and what I discovered was that the price was consistently so high (unless you needed something that’s just +/- program change buttons, and even those are mostly in the $125 zone even secondhand - way too much money for what they are) and most of the controllers were also bigger and more complex than I needed that it made me decide that DIY was the best option and if I was going to build something anyway I might as well build something that would do more. I’ve spent a fair amoutn of time figuring out the best option, and before I found the Pedalino project I was pretty much back to MIDIbox being the only thing that was flexible enough without needing a lot of new code, but it would have still been a lot fo work and the STM32F4 eval board it runs on is hard to get now becuase of the chip shortage.
My latest project “Twisty” - a simple DIY MIDI controller inspired by the MIDI Fighter Twister. It uses the Arduino Pro Micro which is readily available (Teensy is very hard to find these days). USB MIDI and can be easily modified to support serial MIDI as well. Built it to use with my Norns shield but it works fine on PC and iPad as well. Very low power consumption - 40ma or so.
Features:
Easy and cheap to build - Pro Micro, CD4067 mux module, 16 pots, two switches, 4 LEDS, 4 resistors
Four banks of 16 CC controllers - control up to 64 parameters
Easily change MIDI channel
One bank of four CC LFOs, each with controllable rise/fall/duty cycle, three waveforms, MIN and MAX values, cycle range 1/3 second to 30 minutes
Source code and more info: GitHub - rheslip/Twisty-MIDI-Controller: Arduino MIDI Controller inspired by the MIDI Fighter Twister
Overview video Twisty - DIY MIDI Controller inspired by the MIDI Fighter Twister - YouTube
Demo with Norns Dronecaster script Twisty MIDI Controller with Norns - YouTube
I recently built a Teensy-based pedal to control my Organelle while I play the guitar:
The expression pedal controls knobs 1-4, depending on the footswitch that is enabled. The sustain pedal triggers the AUX button.
I use it mostly with the granular freeze patch, using the expression pedal to control knob 4 (wet/dry) and the sustain pedal to freeze the sound.
