Alright, so we come back to what I was suspecting from a while : the problems I am facing since the beginning come from the fact that I don't do things the right way.
I chose the 183MC because of its sensor size and its pretended performances. µ4/3 was mandatory for me, but 20 Mpix are far too much, 16 would have been better - the same as my D4s.
But I thought its claimed framerate would be a good thing.
I'm not familiar with non DSLRs, I would never have thought things would be so difficult. And I know of noone in my neighbourhood who uses such setup, so no way of learning.
When I bought SM OS, I thought it would be the solution of my problems. But despites the wonderful job the team has always been doing, it has never been.
My wish is to have a setup as light as possible. Previously Nikon D4s + (heavy) AFS telezoom + (customized) StarAdventurer classic + PiZW + tablet.
Then ZWO + 3 lightweight lenses + SA GTI + Pi4 + tablet. Much easier to carry and handle - shoudl it have worked.
All my problems so far are related to the camera. I did not try to drive the SA, I even don't know how it will behave and, to be honnest, I fear the worst.
Upon what you wrote, I am going to try and reduce the resolution or the depth and see what happens. On the laptop first, because it is less subject to hangs and I can handle it better, thanks to its KVM, then if I'm OK I will try with the Pi.
The powerbank for the Pi weights less than 200 g and is enough for up to 6 hours, whereas the one I should buy for the laptop weights around 1.8 kg.
I'm sure I did not understand everything, so I will come back and read again your post and Massimo's one to be sure I did not miss something.
Rgrds,

No worries, I am not familiar with the Sky Adventure GTI mount, but that is only because I have never used one. If there are appropriate drivers in Indi (or ASCOM) then it should work. In principal it is a Equatorial mount and it should behave much the same as my Celestron CGEM. The camera specs are what they are and I think the dedicated camera is still the way to go. I have an Olympus 4/3rds camera that I love for daytime images, but I did not find it satisfactory for astrophotography. I never did ask (or you never said) what it is you are trying to image, but a dedicated camera with lens and the lite mount should be a good mobile setup.

I have an old Tamron telephoto lens that I bought an adapter for my ZWO camera that I intended to use for wide field. But in the end I bought an AP65 EDQ refractor that performs much better than the Tamron.

I also have spent many hours getting my system working the way I want it to, but then I have plenty of Cloudy Nights where I live here in Eastern NC to do so. I first make sure I can get the system to perform in my garage (where it is warm) and work out all the issues. so I don't get frustrated trying to do that under the night sky. If you have not already you should check out the "Cloudy Nights Forum," where there are many discussions on all kinds of Astrophotography, from mobile setups to full domed observatories.

Best of luck in your adventure.

I own a few Nikon lenses : AIS 20mm f/2.8, AF 50mm f/1.4, AFS 24-70 and 70-200 f/2.8 and AIS 500mm f/8 Reflex. And a doubler (not a Nikon, unfortunately).
My plan is to use only the 20, 50 and 500 which alltogether weight less than the 24-70.
With the focal ratio, they will result in 54 f/2.8, 135 f/1.4 and 1350 f/8, and with the doubler 270 f/2.8 and 2700 f/16 (forget the 20mm+doubler, too close to the 50mm).
Testing my setup is not easy : I must either do it in the living-room, which is really limiting, but I can power from the mains and stay warm, or drive a few km and stay outdoor in the cold.