So a little update: EVERYTHING WORKS.
Let's start a "Journey Diary - Guide" so that everyone that wants to do it can follow the steps and update. First of all, the previously mega link posted above (here) contains all the files needed. I did everything myself with the help of @Lennart, not diffucult at all, but the responsability is yours alone.
Updating from the ancient 0156 is not that difficult, it's just like any other update for the MIB3, but it breaks Navigation System. This is intentional and it's because Skoda changed the license and offers Navigation as a SWaP now. You can check in the Service Menu (long press menu button) that no 00071C00 FEC is installed and in the supported FECs it doesn't even show up as available to install.
According to the 2 TPI in the mega folder (one older in English, one recent 2024 in Italian) Navigation is now a SWaP, and since it already was included in the car package when bought you can reactivate it using the codes that Skoda provides to re-enable it.
Tool necessary to do the update is any OBDEleven or VCDS or any other tool that can do SVM (Software Version Management), but to re-enable Navigation ODIS-S is needed. ODIS-S is a dealer level software, so you have to rely on a dealer to apply the SWaP or to someone that has ODIS with a valid Geko Online account and the necessary hardware to connect to the car. Just go to the dealer after all the updates, you can bring the activation code or ask them to provide it, is in their ODIS Service Net and can be also obtained from Erwin Portal online.
In the first TPI it's stated that the OCU (Online Connectivity Unit) has to be flashed first. Before doing that use any of the tool to go to the 0075 module (the OCU indeed) and in adaptation you need to change the Crash Signal to "via CAN". Once applied format an usb stick to fat32 or exfat and unpack the version 143 of the OCU update named 5WA035284OCU143.zip in that stick. Insert the usb stick in one of the usb-c port and long press the Menu button for 3-5 sec, reboot in Engineering mode to start the update following the TPI instruction.
Once applied it will reboot and the infotainment will be working as usual. Using OBDEleven or VCDS or ODIS-S you will see that you have a fault error B201A, it's normal when doing an update via usb without dealership computer, it can be easily fixed by updating SVM using a xor tool that can be found here. It's nothing critical, you just have to tell the MIB3 that the software is new.
Now you can proceed to do the actual MIB3 Update: format the usb stick unpack the first sequential package MOI3_EU_SKMQB_R23802P + P26810P + P27800P.7z in the root folder, go in the Service Menu and then press Update. The software will auto check the usb drive and since everythin is signed by Skoda it only applies if the file is the correct. It is almost an 1h job and it will reboot multiple times (5-6 at least), since it's not incremental everytime it has to delete the previous and reflash.
After this you will land on SW version 278, MIB3 will work fine except that Navigation wont start. If you go in the Service Menu you will see that the Predictive Navigation FEC 00071C00 is not installed but it will be present in the available tab that was not present before. You can do a SVM fix again.
Re-do everything, format the usb stick and unpack MOI3_EU_SKMQB_P30600P_0306.zip, apply again in the Service Menu and wait for it, will probably need 20-25 min. On reboot, do the same with version MOI3_EU_SKMQB_P30800P_0308.zip than you can find here a then again with MOI3_EU_SKMQB_P33000P_0330.zip that will bring you to the latest 0330 version that was released i think Jannuary 2024. Remember that after each upgrade you have to confirm the installation change.
Once done you can finally check if everything is working except of the Navigation System.
To fix this you have to enable FEC 00071C00, and as said it can be only done by adding your specific activation license code and unlock pin (that work only in your car and vin) and only using ODIS-S Online, so if you go to a dealership to activate it he surely can and already has your data to do so, else just bring the code with you and let them restore it. It can be found in the excel sheet in the mega folder, just search for your vin and you will find it.
If you have the necessary tool to use ODIS-S yourself (like i did), connect to your car and perform a FFS (Function Activation), proceed with option 1, enter the 3 values when asked and apply them, it will ask you to login online using Geko (DSS Login) and let ODIS-S check with the servers if the codes entered are valid, after a 20sec wait or so it will be verified and unlocked. Now Navigation will start again! You can check in the Activated FEC and you will see that 00071C00 is enabled and valid.
This is not a hack, it's not some sort of dark magic, is just exactly what the dealer does when they perform an update. Since they often wont do it (if aint broke dont fix it) or refuse because "risky" now you know that you can do it by yourself, files are publicly available if one know where to look and how to find them. And since the latest update is not cumulative you cannot apply the latest to a very old version they would charge you a lot of hours to do it.. well actually it is cumulative but it wont apply because security check will not pass so be patience and follow the TPI.
Enjoy.
R.