Can you take some pics of your setup and the macroboard? Something doesn’t sound right.
USB otherwise working with some devices?
I am so glad I found this post. That gives me some hope. I also purchased the Sayobot OSU mini keyboard and while it works for copy past etc, it can’t be setup for KVM because it is simply not recognized by KVM as keyboard and the keystrokes are not interpreted as they should. Initially I thought it’s settings so I played without end with the Sayobot application but nothing worked. To be honest the site sucks from Sayobot but I don’t blame the developer if that is something that is being provided for free. As with everything in China, there is no intellectual property and respect in China for anything that anybody else created and so if it is the case that Sayobot is a community project, then the 100’s of sellers of hardware keyboards just ripping off that effort of that single person or a few people. In any case it is impossible to contact anybody for support, the wechat or whatever contact there is dead end, nobody knows even in the OSU forums, it seems most OSU players are moon-walkers. There are millions of OSU keyboards like the ones sold every moment, sending you on a spin through search of proper software (half in Chinese, but even that Chinese description is crappy, like it was done by a sleepy programmer with a headache from a hang-over). Somewhere it graciously mentions you can even load scripts into the keyboard and there are voluminous pictures on how to do it but that site is down and another site show application that has no sign of script support whatsoever. It’s all just junk in haste put together by Chinese developers and manufacturers there just flood the market at any price and suck as much money as possible.
Enough rant.
I hope the suggestions here will solve my problem which I have - very graphically with a extensive chart show in the Reddit post. I can’t include link so I just attach the screenshots.
So I cross my fingers.
@wendell : Happy to post some pics – what do you need to see?
And yes, my other USB devices seem to work okay. For example, I normally have my keyboard plugged into a USB 3.0 hub, but if I plug it into a HID port instead, the KVM does respond to hotkey switching from that keyboard.
Qmk on the macroboard? 5ms delay between keypresses?
Does it transmit the keys otherwise? (Program one of tlbuttons to type E and see if it goes into a text editor?)
I’m not familiar with QMK – can it be run on any macroboard? I’m just using the software the manufacturer provides on their website. I’ve tried delays between 5ms and 50ms, and it doesn’t seem to have any impact.
Yes, it does transmit the keys otherwise – but not through the HID ports of the KVM. If I plug the macroboard directly into my computer, the keys seem to register fine.
I’m so tired of buying macroboards and reaching all the way under my desk to switch inputs, I’m actually considering buying this X-Keys board, since it has firmware intended for KVMs and the support team is in the States… but the $110 price tag is making my eyes water. 
The falcon rgb8 was $15 when I ordered it and it works fine. $100 is way way too much I agree
Alright, a final update for anyone who appreciates closure. I decided to try one more cheap macroboard from Amazon (this one). It was an improvement in that the keystrokes actually registered through the HID port on my KVM, but the KVM itself still did not recognize the hotkey macro.
So I finally broke down and bought an X-Keys product. (@wendell: Thanks for the suggestion of the Falcon RGB8, but I was pretty dedicated to finding a solution that wouldn’t create “one more thing” on my desk to clutter it up and catch dust. It’s for that reason that I’d been searching high and low for a minimal board with 2 or 3 keys that I could just attach to my primary keyboard with some double-stick tape.)
Rather than buy the $110 4-key X-Keys board to which I linked above, I actually ended up buying the X-Keys USB3 with KVM firmware. It saved me a few bucks over the 4-key pad but more importantly, it allows you to trigger macros with any momentary push-button switch. And that in turn allowed me to drill said switches into the front edge of my desk for a completely clutter/dust-free setup. And the LEDs in the switches make the whole setup look really cool.
Programming the X-Keys device was a snap; had it done in about 60 seconds with absolutely no troubleshooting needed. It just worked. So I can confirm that X-Keys, with the KVM firmware, definitely works with a L1T KVM. (Note that if you want an X-Keys device with the simple KVM firmware, you have to buy it that way from them – the manufacturer informed me that they will not provide the firmware to customers to flash themselves. And for some reason, their devices with simplistic KVM firmware are more expensive than their devices with the standard firmware. C’est la vie.)
