How about sending to 255.255.255.0, or something like that? I think you can broadcast a message to all devices in your network this way.

I don't know what [fffb~] does, but [uzi] can be replaced by [until] connected to a counter (which can be created with [f ] and [+ 1]). What does [zl group] do?

Don't you also need the -open flag? Also, why do this as root? Why didn't crontab work? Can you share some scripts you tried?

I don't think there is such a library. Maybe Ofelia integrates Lua in a way that could sort of make something like this work, but again, that's in Pd. Dunno.

I guess a W32 package for Pd is a 32-bit Windows Pd executable, which you can get from Pd's website. If you're on Linux, you can run it with wine, to test that your external really works as expected.

[pdcontrol] is a vanilla object. I can't remember when it was included, but it wasn't long ago. There's a chance your Pd is quite old, especially if you have an old Raspbian image, and you installed Pd with apt-get. Either compile the latest Pd from sources, or get a newer Raspbian image that will get you a newer Pd with apt-get. Then you'll be able to load [pdcontrol].

Just replace the strings "X = " with something with one white space only, at the end. Then make sure in Pd the argument to the [receive] object that receives the value is the same as this string without the white space. Also, get rid of the tab character in the Arduino strings ("\t"). Do this for all strings.
All this if the Pd patch uses the [serial_print] abstraction. If not, I don't know what else is wrong if I don't see the patch.

I suggest to change the printing lines to the old version. If the Pd patch uses the [serial_print] abstraction, the new version will cause problems because of the additional white spaces.
I guess the patch uses the string that is printed first as a tag (possibly also as a name for [receive] objects.

I came up with a pretty complicated solution, but it seems to work. Here it is both as an image and an attachment.

randomly_select_toggled_values.pd

@KMETE you have to put all objects you want to run at a 1-sample block size into a subpatch. [dac~], [s~ ], [r~ ] and the likes can't handle block sizes other than the default 64. Only [inlet~] and [outlet~] can up/downsample signals.
Also, you don't need [delwrite~]/[delread~] there, but a [array define fed 1]. Get rid of the objects on the right and the top part of your image (with the [delread~] and [delwrite~], along with their connected [tabsend~ fed1] and tabreceive~ fed]), and change the argument to the [tabreceive~ fed1] to "fed".