anyone know when we're getting the 1.4.0.4 update?

It is currently available if you're using gog galaxy. Sadly no offline installer but it should be soon (guess based on how fast we got the previous patches as offline installers).

Can't play on other servers though. The reason I bought it on GOG is that I don't like DRM :(

Playing on another server would fall under multiplayer...

Have some patience ...Today is Sunday so gog doesn't work today....Probably they will be available Monday or Tuesday...

Linux user here, can confirm v1.4 took a big dump on my frame rates. I've been eagerly awaiting some re-optimizations, hopefully this patch delivers when GOG deigns convenient to set it up for download. It better be worth the wait.

That sucks, what's even the point of buying this game here if it's DRM-free version always late, and you need a client to play with steam users anyways?

That's how it always was before the galaxy client...But now for people that use galaxy it is easier to have the patch at the same time as steam...Imagine that there are 20 games updated in one day...How can gog make offline installers for every game the same day?

Maybe release the update as a standalone zip file that you drag and drop into the folder (not an uncommon thing) or have a bot that auto complies the updater DRM free version. In fact making something DRM'ed takes longer, so your point is silly at best.
Also as I said, what even would the point be of buying it here, rather then steam?
Honestly just not having the update always be 1 version behind would make a load more sense at the very least, that way you could at least make a dedicated server that non-gog uses could also play on. As is, this's just an inferior product that cost more (Steam version goes on sale every other month for 4.99, here it's been full price for years) and has zero benefit over the steam version, so I fail to see why anyone should buy this game here.

New offline installer available for those interested.

Unfortunately, to the extent that I can even test easily (v1.4.0.4 inexplicably places the frame rate counter below the window at high resolutions), I'm not seeing any real improvements in frame rate with this new patch. Really sad to see a game my hardware used to be capable of handling now run so poorly it's hard to enjoy in certain places.

Hi Afdal, I also use Linux (Mint 19.3). On my six years old PC Terraria 1.4.0.4. runs very smoothly in 1920x1200 resolution. No Problems at all.
The only thing is, I can't play it full screen in my native screen resolution (2560x1600) because the 1.4.0.4 Linux version currently does not supporting this.
Maybe you should check your graphics driver or generally your system.