SS4 install fails!

[SpiritLevel]

Hi all.

I've just tried to install various versions of SS (4.0.6 and 4.2.0 through to 4.3.0) without using a .env file and I keep getting an error during the install that complains about line 730 in Filesystem.php.

EDIT: I am able to install SS 3.7.2.

Here is a screen shot showing all install requirements are met:

Here is a screenshot of the error message the installer gives:

[SpiritLevel]

Well it appears .env needs to exist (and possibly be empty) and be writable in order for the installation to complete...