There's another update:https://imgur.com/a/6sczBp4

This one took awhile, despite being only 523MB. There's no info about this on the launcher, GOG patch notes, or the website.

It recently started downloading automatically for me, but it started at 62 out of 63 GB. So you likely aren't downloading the full amount, it is just a weird display error.

this patch is in fact a new build, yes it corrupts saves so don't install it until you are ready to start a new character guys

There has been another patch since the one that corrupted saves.

When they made these notes on steam forum ..
https://steamcommunity.com/app/1086940/discussions/0/2971771480507957282/

.. There was an edit near the bottom of the post which mentioned the patch was being rolled back, due to the save corruption issue, GOG Galaxy then rolled back the installation to the previous Hotfix#3, then I saw the uploaded public files updated ..
https://steamdb.info/app/1086940/depots/

.. the post on steam forums was edited again ..
"EDIT: This patch has now been re-deployed. Thank you so much for your support!"

.. and then GOG Galaxy installed the new patch once again. (GOG Galaxy grabs the same files as steam)

If you still have problems with saves, either you have not got the redeployed Patch#1, or Larian Studios have maybe not fixed all instances of save game issues.

The latest which GOG Galaxy installed for me which I mentioned a few posts back is working fine here.

I'm finding this new patch is great. Everything runs a lot better. There's still bugs to squash, but the difference between this current patch and release is night and day.

Is it me only, or has the loading time decreased after applying the Patch?

It starts long ago:
https://www.gog.com/forum/divinity_series/divinity_original_sin_2_definitive_edition_patches_links_for_gog_downloader

Patches have same size as full install even for tiny fix.

When GOG updated my game with patch 1 a couple of days ago, it was about a 400mb download, so the patch isn't big, neither was the hotfixes.
But when they reverted the patch, GOG started to download the whole game again, so 62 GB..
On steam people said the reverting started about a 800mb download.
So don't know what¨'s up with GOG and updating. Seems much better at Steam.

And today my play button for BG3 was grey, so used verify/repair install, and now it started downloading the whole 62GB again..

Almost makes me want to buy the game at Steam..

Is it me or is the update taking a very VERY long time to patch?

edit. definitely, the patching is taking longer than it took me to download 63GB and install the game!

Yes, but how long did it take to patch the 523mb file? MIne hasn't even started patching from 2651 to 3931 yet and I've been at this for 2 hours already :-(

It needed 1,5 hours.
After installation I haven't seen any big difference in the game.

Again, it is not a new problem. Here quotes from 2018 tech support answer about patches for gog downloader:

"As for Divinity: Original Sin 2 and Bard's Tale IV, I have investigated the issue and unfortunately they turned out to be special cases. When we received the patch for Bard's Tale IV, it was a massive content chunk of over 20 GB. The standalone patch would have been the size of around 60% of the base game and would have come in several 4GB chunks, just like the base game does anyway. For technical reasons, we have never generated standalone patches, and only updated the game installers themselves.

Same goes for Divinity: Original Sin 2 after the Definitive Edition was introduced -- the size of the game has increased drastically, and standalone patches were never created. In both cases the difference in sizes between the patch and the updated installer would have been negligible".

Now (according to Galaxy) I don't have enough free space (40 Gb) for 523 mb BG3 patch.

Sorry for this stupid question but is the version 4.1.84.2021 now the newest version after the patch or not?

Yes it is.