I can test VK and Facebook, also happy to create an account at Tumblr.

Thanks Adam. Feel free to try installing v11 again from Git and see if it works!

I tried a couple of days ago and managed to install on localhost, so that's good. However the menu modules and other key modules and blocks were claimed as missing so I couldn't really do much after that. Will try installing on my hosting account later this evening though.

Stuck on Step 7 of installer:-
localhost gives no error just times out
live hosting gives the error "Parse error: syntax error, unexpected string content "docs/pages/comcode_cu", expecting "]" in sources_custom/hooks/systems/addon_registry/composr_tutorials.php on line 1577

Also of note, I use peazip and I have errors extracting the v11 tar or zip. Unspecified errors but thought I'd mention it.

Patrick/Adam, could you connect on this, maybe set a time to do a screenshare session or something and hammer through whatever bugs come up?

That line "line 1577" sounds like maybe you extracted from a TAR file that had not fully downloaded.
EDIT: The issue about missing blocks and modules likely also would have been caused by an incomplete download.

The issue with Peazip is now fixed. There was a symlink in the Git repository, which didn't agree with Windows. I've removed the symlink and added it to our testing for that to not happen again.

Still timing out on Step 7 after a long wait when step 6 completes on local, uploading to live... happy to be involved in a bug hunt but I'll let Patrick pick time and date.

Installed on live, I did notice the installer put a port 80 addition despite not being on localhost. Onto the share testing...

Can you clarify about port 80. Do you mean it's in your base URL? Maybe show a screenshot of what you mean.

As for installation timeouts, I've just done some benchmarking and optimisation but I can see more is required. Step 7 is 13 second son my machine, Step 8 is 20 seconds.

Sharing works to all 3 services and previews/end results are what would be expected, though it selects a random header banner as the post image so that will need defining (a default for text only content?). Tumblr lets me select a header banner or the advertise here banner ;)

Up and running v11, yay. Yes, Port 80 was added to the base URL by the installer on my live hosting but I noticed and removed it.

Thanks Adam.

Just on the installer again...

I've optimised it to Step 7 as 10 seconds, and Step 8 as 12 seconds. So roughly 1/3 faster.
I'm not too worried about the installer performance from Git given that there is a lot more to install from Git due to all the non-bundled addons being included. But users may use some very slow servers so it was worth taking the chance to make the gains I reasonably could.

Nice, will retry on wampstack this evening.

Regarding social services using the header image...

There's some code in HTML_HEAD.tpl:
{+START,IF_EMPTY,{$METADATA,image}}
{$SET,fallback_image,{$IMG,logo/standalone_logo}}
<meta property="og:image" content="{$GET*,fallback_image}" />
<meta property="og:image:width" content="{$IMG_WIDTH*,{$GET,fallback_image}}" />
<meta property="og:image:height" content="{$IMG_HEIGHT*,{$GET,fallback_image}}" />
{+END}

It says to use the logo for the Open Graph image if there is no natural image on the page (natural image might be the images associated with the news article being viewed, for example).

The Facebook tutorial contains a section "Vastly simplifying the images", which shows how to make a new custom Open Graph image, should you want better than that. I'm renaming that tutorial "Composr Supplementary: Facebook Support / Open Graph" to indicate it also documents Open Graph (which is Facebook's system that they standardised and is now widely adopted).