@atux this message means that the connection between the first outlet of the third object in the patch env.pd failed to connect to the first inlet of the eight object in the same patch. The third object is an [inlet], I guess, and the three question marks mean that Pd don't know where this is supposed to go.
A possible reason is that you changed something in the original patch (an object name, or an object might have loaded from a different library, for example), and now the inlets/outlets table is not the same as it was, hence some connection might be sort of lingering. Don't know if my explanation is clear or not.

You can add this to your startup flags by going to File -> Preferences -> Edit Preferences, and choose the "Startup" tab. At the bottom of this window, in the "Startup flags:" entry, type "-audiodev 2" (at least this is what I had to type), and then relaunch Pd to see if it chooses the right device on startup. If it doesn't, experiment with the number, which should be the same as the position your device has in the list of your screenshot (I thought this was 1-based, but it appears to be 0-based, so the first item in the list is 0).
Even with this flag by default, if you want to launch Pd from the terminal with another device at startup, you can still do it, as the command line flag will override the one you have set in Pd's Preferences.

Before attempting to install anything, like pipewire (I'm a Linux user and have never used it, TBH, it's the first time I read about this, didn't know it before), go to Media->Audio Settings, and try to choose another input and output device. It may be that the device Pd chooses by default is not working. It might also be that you get two devices with the same name. That's the case with my laptop, where I have two "HD-Audio Generic" entries (actually four, two tagged as "hardware" and another two tagged as "plugin"), but the first ("hardware" tagged) doesn't work, while the second (again "hardware" tagged) works fine.

@jameslo while it is not necessary to add the forward slash, it doesn't really hurt adding it, so it is not necessary to remove it. Actually, I think it's good to be there as it explicitly shows proper OSC addressing.

Do you really need to record at your baud rate? A high baud rate enables fast transmission of data between devices, but do your data really change that fast?
Perhaps you can filter your data and save every time there's a big enough change in the values, or something like this.

Paid gig. The publisher of my first book, "Digital Electronics for Musicians", has asked me to write a second edition of it, with updated software and all. This book is about interactive musical projects with Pd and Arduino. We are looking for a technical reviewer, that will read through and realize all the projects, to verify that what I've written is functional.
Even though an introduction to both Pd and Arduino is made in the book, experience at least with Pd is highly recommended. Experience with the Arduino is desired.
Please DM me if interested.

Actually, raising the window size should drop the CPU usage. I tried your patch on my laptop, and with a 4096 size, I got a 13% CPU. while with a 16384 size I got 10%. With a 2048 size I got around 17%. I didn't get any dropouts or crackling sounds at all. Are you outputting all the subpatches at the same time? If so, did you try to lower the volume of these sub patches? It could be that they are exceeding the audio range and there is distortion there, but I doubt that this is really the problem. Other than that, I think @whale-av gave all the help possible.

@whale-av I think you got this covered much better than what I would! Honestly, I really don't know why you think I would know more than you..

Can you share your patch?

@whale-av That is a bit beyond Pd programming though, as Automatonism (which is great, and sometimes I do use it for teaching and trying to get people into Pd) conveniently packs all the programming into its abstractions.
@henrique99sl I don't know the specifics of your assignment, but asking for people to just send you patches is definitely not netiquette, so I would advise you to refrain from asking questions like this in community fora, like this one. As a reference, here's a post of an older admin of this forum (Maelstorm was an admin, right?) about this.