This has been asked several times already (I found it here, here and here), but basically everyone simply recommend to perform a full install to the USB stick. But I do need it to stay as a LIVE session, not a "full install on USB", for a number of reasons (the most important one being that using Live session I can easily install Ubuntu using the desktop icon)
So, my constraints for skipping the Welcome Screen (and automatically choose "Try Ubuntu" option) are:
It must actually be the Ubuntu Live session (or as close to the default as possible). Same software selection (gparted is present in live sessions, gimp is not, for example), user (name and ID), behavior (no login screen, no password for
sudo, to name a few), no GRUB, etc. That rules out an Ubuntu full install on USB.
It must be able to install Ubuntu in the computer (while full install requires the ISO file, an additional USB stick, and the hassle of Startup Disk Creator)
If possible, to be as fast as the "text-based launcher" (the one you have when you press a key right after the kernel loads)
It must be completely automatic, unattended from boot to desktop.
Select a different language than default. It can be a hard-corded selection (actually, it must, since boot itself shall be fully unattended). But preferably be easily changed ("easily" as in editing a config file then rebooting)
Is it possible?
The proposed (great) solutions that I've ruled out so far are:
Installing Ubuntu in the USB stick (for all of the above mentioned reasons)
Ubiquitypackage (it removes the ability to install the system from that USB as well)
Ubuntu Customization Kit (ubk): several limitations and caveats, and its not even in the repos
Remastersys / LiLi: its the same as full direct USB install, only customized.
An ideal solution would be something like "create USB sick using Startup Disk Creator, then open it and remove / edit / add file(s) xxx, yyy, zzz"