Am using offline downloads to try to get past the 92% download bug since galaxy seems to be absolute doodoo.
It doesn't help that there are posts dating back to 3 years ago regarding this bug with various other games which does not really inspire confidence.
Turns out the offline downloads aren't the most up to date either. Hotfix 3 is missing.
It doesn't help that their official solution for the 92% bug is to download the offline installers but they don't even maintain it to be the most up to date.

First time using gog because it's DRM-free but it has been a bad experience all around so far.

I’m having this issue as well. My friends are playing on steam, so we can’t start until the offline installer is updated. I’m starting to regret buying the game on Gog. What’s the point of a DRM-free game if you’re essentially forced to use Galaxy to play the latest updates. And even that has the tendency to not work

Same here, really.
There's always a big delay for the offline backup installers... and GOG doesn't seem to care one bit?
We always have to wait longer when GOG is proudly boasting about being DRM free, but can we then say that it is really the case? It's a bit disheartening to be honest. It shouldn't take so long to make an offline thing available, especially when it must be a couple hundreds MBs and when it's already available via GOG GALAXY. It's like they only release a patch when the next one becomes available, I hope it's not on purpose.
I've even sent support tickets regarding this issue to both GOG and Larian, but to no avail so far as they seem to be ignoring me?
Maybe we need to make more noise now, hmm.
Hopefully they're just like crazy busy and will get around to it, or maybe the situation will improve when we get actual updates instead of quick hotfixes! One can only hope... but it's definitely a shame having these kind of issues stain the release of such a GREAT game!

There's no reason you can't use both the offline installer for the main install and Galaxy to apply hotfixes ASAP.

GOG originally just sold old games that never or very rarely got updates. For new releases, the offline installer model is not a great fit to keep up to date. Once the game is actually finished, the offline installer will be a great choice though.

Will the patch update get stuck at 92% again? Am only using the offline installers because their crappy app is borked.

I don't know. But all the updates have worked via galaxy for me. And they only take like 30 seconds.

Same issue trying to play between gog and steam users. Hope this gets released soon so we can play together this weekend.

Well, you can see an update happening in Galaxy when it does it. If you mean the specific version# you could check the builds here:
https://www.gogdb.org/product/1456460669#builds

If you used the offline installers up to Hotfix 2.1, then the Galaxy update to Hotfix 3 should work. It worked for me on two different computers after using the offline installers.

Updates through Galaxy usually work with offline installations - though it may be that you need Galaxy afterwards to start the game.

To update an offline installation via Galaxy you need to install Galaxy and start the game via Galaxy - then it should do the update process.

I had it once that a game no longer started by itself and i needed Galaxy to start it up but the others all worked still without Galaxy.

Hey - That's a surprise! I never expected that to happen!

Hotfix #3 (v4.1.1.3636828) is not yet available as stand-alone installer. And you are forced to use Galaxy if you want to update? That's unexpected!

Yep I'm a bit sarcastic here, sorry. Don't mind this old-timer, that knew GOG from a time when they where more active for off-line installers. Even from a time Galaxy did not even existed. Ahh - Those where the real Good Old times.

Anyway - This new up-date has loads of bug fixes, so it's a nice one. Maybe Monday or Tuesday we will get the off-line installers. I still do not want to use Galaxy, so I guess I (and all other off-line installer users) have to be patient.

I get this error when I try to apply the offline update to 2.1.

Game patch log
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\bin\bg3.exe
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\bin\bg3_dx11.exe
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\CrashReporter.dll
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\DriverVersionChecker.exe
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\LariLauncher.deps.json
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\LariLauncher.dll
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\LayersChecker.exe
Error modifying E:\Program Files (x86)\GOG Galaxy\Games\Baldurs Gate 3\Launcher\Shared.dll

My friend resolved that by installing the game somewhere else than in Program Files. Actually, you should avoid installing any games in there as it can cause a whole heap of issues like with permissions. :/
You should be safe with anything at the root like E:\Games\Baldurs Gate 3\ for instance if you like having you games neatly grouped like I do ;)

Yes, do not ever install games into C:\Program files\...! Always either into C:\BG3, or better yet, into another partition altogether. My partitions go through Q\....;) Sequentially. (I have a lot of drives...;))

Also, Galaxy works great, and you'll always get your patches and other things much quicker than in offline installation files. BTW, Galaxy installs are not DRM in case you were wondering--you can run Galaxy installed and updated games directly from their exes just like from the offline file game installs, no need to run Galaxy every time you run the game--there's no difference, except that Galaxy is a much quicker proposition all around because you don't have to download offline files and then install them, in two separate operations, as Galaxy installs as it downloads.

I use Galaxy for initial game installs and updates. When the game receives its final patch (in the future) then I'll download the offline files and save them as my legal personal copy of the game. There's no sense in downloading the offline files every time Larian releases a patch, is there? Sometimes GOG supplies stand alone offline patches, but sometimes you have to download the entire game again! Galaxy is much easier and quicker, imo.