A user who has switched to the "beta" branch of Simutrans-Extended on Steam has reported (https://github.com/jamespetts/simutrans-extended/issues/687#issuecomment-5830332616) the following:
Quote from: userFATAL ERROR: roadsign_reader_t::read_node() - version 0 not supported. File corrupt?
Aborting program execution ...
This is a symptom of a pakset incompatibility.
Not having set up Simutrans-Extended on Steam, I do not know what the setup is, so cannot understand how this can be happening. Can anyone set out the position
vis a vis Simutrans-Extended on Steam, what the "beta" branch does and how the paksets are set up.
As far as I'm aware, the Steam release exactly mirrors the nightly build of simutrans-extended/master - it is selectable in the Betas menu. Without seeing the exact setup, my guess is that the game attempted to load a Standard save in Extended because the savegame folder is in Documents and not the main steam directory. If so, then the problem should be fixed by launching a second time.
As far as how the paksets are setup, the nightly build only includes Pak128.Britain-Ex, so when opening the game there is no pakset selection dialog and it immediately tries to open a save.
Thank you - and thank you for responding on Github. That is helpful.