bliznik: Huh?
I thought so long as the game uses Sierra's patch system, it should be compatible with ScummVM. I'm unsure how the patch breaks anything in ScummVM.
I thought ScummVM was already tested with GOG's version, which includes patches.
Yes, patch files will be applied, BUT when the fan patch contains errors like for example uses uninitialized temp variables, it may cause an issue in ScummVM, because ScummVM checks for these kind of errors, as well as checks for tons of other script bugs. Plenty of these fan patches do contain errors (no blame here, most were created ages ago when no detailed knowledge was available).
Worse: when it is a recompiled script, there may be other issues. Or even issues that were already fixed, but are not detected anymore because offsets have changed.
The original interpreter didn't care about any of that. It simply tried to execute and went on and on, sometimes resulting in internal memory corruption further down the line. That's even the reason for all these script checks inside ScummVM in the first place.
And thus you should not use fan patches, because these should not be needed in the first place. You can of course still use them, no one is stopping you, but if there are problems well, and I remember there at least were problems with QfG3 fan patches and people couldn't just remove them, because that broke saved game compatibility and thus their saved games would have been worthless.
For example timer bugs should not happen in ScummVM anyway, because ScummVM contains a speed throttler, which makes sure the game doesn't run way too fast internally.
And tons of script bugs are patched automatically within ScummVM, without you even knowing that these issues got patched and these on-the-fly patches get applied to all sorts of different versions too, like for example the localized (French, German, etc.) versions of QfG3. Using the common fan patches in these cases will typically result in crashes, because the patch files are simply not compatible (has nothing to do with ScummVM, the same will happen in Dos).
Especially the NRS patches are GREAT for the original interpreter.
But you should not use them under ScummVM, because they won't really fix anything (to my knowledge) that isn't already fixed, and may cause harm instead.
I think some patches are even blacklisted, I would have to take a look which ones were blacklisted.
ScummVM is supposed to make these old games just work, without having to fiddle around with fan patches.
And if there are still game bugs left, they should be reported to the ScummVM bug tracker, where they should get fixed the proper way (internal script patcher). As I said that has tons of advantages, especially that localized versions are fixed as well.
Also: these internal script patches within ScummVM WILL NEVER DESTROY SAVED GAME COMPATIBILITY. Tons of these fan patches do destroy saved game compatibility, which is an utter nightmare, especially when you want to get rid of them.