why I can’t disable sound delay on the Sonos Port line input?

Never.
The sound delay, as far as I understand, is needed for sound synchronization in party mode in adjacent rooms or lip synchronization if a TV is connected.
Sonos streamers and not only Sonos I install exclusively as zonal streamers for airplay.

Problem or not (for some), there's a legitimate reason for it, and it's not going away because removing it causes far more problems for Sonos' core features than it does for edge cases that Sonos simply wasn't designed for, nor marketed towards.  

Long story short, if you are looking for a live performance speaker with no delay, buy a speaker designed for live performance with no delay.  Don't expect one which is specifically not designed/marketed for that type of use to accomodate your needs.  

As to using Bluesound, it's also going to have a delay.  Any multi-room streamer will.  There's simply no denying the laws of physics.

I suggest again, read the threads.  It's explained several times.  Hint: Streaming in perfect sync to multiple rooms/devices requires the buildup of a buffer in order to ensure reliability with no dropouts. 

That’s a pretty big hint! 😜

Bluesound also will have a delay?
Wait, maybe I don’t fully understand the reason for the delay?
It seemed to me Sonos for some reason did this on purpose and did not want to made a settings equal to 0 seconds.
To be clear, we're talking about the delay of analog audio that is sent to line input of Sonos Port and passed through output.

Thank you, I read everything carefully. But I don’t really understand your slightly irritated tone.
I would like to know why there is a delay. Is this done specifically at the software level or is it a hardware limitation related to analog-to-digital conversion.

The delay is to enable synchronised multi-room audio. This was (AIUI) the business model for Sonos when the company first established. Whilst they could, I expect, develop a speaker without a delay, why would they? There are thousands of that type of speaker. And it’d be a single speaker, so that hardly fits Sonos’s business model. 

Frankly, I’m staggered you still don’t get this, since you’ve been on these forums for more than 10 years and you say that you’re an installer. How can you install kit for all this time without having a proper understanding of it? 

The delay is to allow for buffering for multi-room streaming and sync.  What is so hard about that (and where was it not explained, several times already, in those linked threads)? 

As to software vs. hardware limitation, why does that matter?  It’s a necessary function of a core capability of Sonos (and other) multi-room streamers.  Knowing if it is software based or hardware based is just so you can argue that a software based buffer means Sonos should compromise that core functionality for your anecdotal case, something they are not going to do (and haven’t done in the going on 20 years that people have been asking for it). 

Maybe I'm wrong and there will be a similar delay on all devices, which means I will need to reconsider my installation scheme.
The fact is that in the pool I have a smart speaker with a voice assistant, but at the same time it must transmit sound to the ceiling speakers. Therefore, the second speaker combined into a group is located in a rack and is connected to the sonos via the linear input, which is connected to the parasound amplifiers. But when I listen to music through a smart speaker, the sound from the ceiling speakers is delayed and it is very noticeable. I can’t completely turn off the sound of the smart speaker in the pool because through it I listen to answers to voice commands and questions. (synchronization of voice responses with the second speaker in the group is not provided)
And the systems should also provide the ability to stream from a smartphone via airplay, which is why I install Sonos.

In a word, everything is complicated and confusing.
I'm not sure that anyone could even understand what I wrote in my poor English.

Good Lord, what is it that you do not understand??????   The analog line-in source is real time.  In order to stream that source to multiple rooms in perfect sync, that real-time source must be buffered, so any transmission problems; dropped packets, interference, sync adjustments, etc. can be corrected and processed before the buffer runs out and a dropout occurs.  This goes for every real-time source streamed to any multi-room synchronized streamer, including Bluesound.