If so, how I get them?
GOG client failed while trying to update.

It is not a stable version yet so it is not available through GOG.

» How to enable experimental updates?
The way you enable experimental updates is depending on where you downloaded the game from.
If you downloaded the game from factorio.com or GOG, go to the ‘Other’ settings (Main menu -> Options -> Other) and enable the ‘Enable experimental updates’ option. After restarting the game, you might need to enter your credentials. If you don’t know what credentials to enter there, read the paragraph “What credentials is the game asking for?”

» What credentials is the game asking for?
When the game asks you to enter some credentials, you have to enter your factorio.com credentials in order to access the Multiplayer Matching Server and/or the Mod Portal.
If you already have an account on factorio.com, just enter its credentials and continue. If you don’t have an account, you can create one by pressing the ‘Create account’ button.
This only works in the multiplayer menu on the Steam version when trying to access the Multiplayer Matching Server (‘Browse public games’).
If you bought the game on Steam, you can create an account by pressing the ‘Sign in through Steam’ on the factorio.com login page.
Please check if the account is actually linked by going to your profile page (click on your username in the top right corner) and, if necessary, link your account there once more.
If you bought Factorio on GOG, go to your GOG account and click on Factorio. Press the ‘More’ button and click on ‘Serial keys’.
Then create an account on factorio.com or, if you already created one, log into that. On the profile page, click on the ‘Upgrade’ button next to ‘Membership’ and enter the serial key from GOG in the text box.

This is not true. If you don't mind using galaxy, you can enable 'experimental' beta branch and get 0.17 through normal GOG channels. It lags a bit behind the latest (right now latest is 0.17.52 while galaxy only offers 0.17.49) - gog version seems to only be released about once every 14 days.

I didn't find a way to download mods without having factorio account, so you may still need one - just not to get the base game.

Now that .17 is stable, there will be a normal (ie. non-Galaxy) release right? It's been so long since the last I fear it might genuinely be forgotten.

Until now the Version is not up to date.

It is now available. :D
Thanks lovly GOG team. ^^

You have 0.17 installer available for download? I cannot see anything new in my account

The current stable version is 0.17.69. Looking in my library I see that the versions available here is 0.16.51 for windows and 0.17.41 for linux. Don't know if it is same on galaxy.

@jmd3au1 It was a total normal update for me. No idea why. ^^

0.17.69 is available as an executable download now. Thanks GOG!