I tried firing up MacMediaKeyForwarder on an external SSD running the last public beta build of macOS 26 Tahoe, 25A353 (the Release Candidate that will likely be sent of to distribution to the public tomorrow), and it causes the UI to become extremely unresponsive after trying to use the app and opening the menu to access its options.
On the first few attempts I could still kill the process from Activity Monitor, but on my last one I had to resort to killing it from the Terminal, as not even that would work.
I know this fork of MMKF is, at this point, abandonware, but I felt it would be important to warn other users to not attempt to use it on Tahoe, as it is no longer likely to work.