Well, since this game is not shooter nor action one, there is no point to load our graphic cards to produce 1000 frames per second. Is it possible to GOG to install a small hack into game to limit FPS? I know that RRT3 engine does not support vsync, so just hard internal cap at 60 is suffice. It's not about external 3rd party frame cappers. Is it possible? GOG specialists have already done a huge pile of various hacks and fixes to games presented here.

One option is to use dgVoodoo2, "a wrapper for old graphics API's for Windows Vista/7/8/10" made by Dege. Recently on that site there has been announced a partnership with GoG. Personally I don't know any other details. Will there ever be specially customized wrappers for already released titles? I wonder.

I do know that this game runs a lot better with the ready-for-download dgVoodoo2 wrapper, the game's graphics option to "Disable Hardware Transformation & Lighting" doesn't need to be ticked while running on the latest machines and in consequence graphics look a lot better and the game runs faster.

When using the wrapper use the maximum VRAM for DirectX, that's 1024MB, and also there is the option to Force vSync which will give what you want, a hard limit at 60fps.

I forgot a detail of using dgVoodoo2. GOG added a custom dll file (d8tx.dll). You can't run the game without it, but it gives conflict with dgVoodoo2. The solution is to delete that file, then take a copy of the D3D8.dll file that you will have placed this file in the game folder during dgVoodoo2 install. Rename this copy as "d8tx.dll", and the game will run.

I agree it would be nice if GOG would customize the wrapper specifically for the game cause this step means it's not quite plug-and-play.

Personally, I use Riva Tuner, and it works fine. I am just upset that limiter is not in the box and require additional hand moves.

I just want to add that I'm using DxWnd for this specific purpose, limiting the game's framerate. It is one of the few tools that is compatible with Linux+Wine.
Also, when I still used Windows, I used to use a tool called DxTory for that purpose as well, limit framerate.

Is all the above still true? i have been trying to get a GOG version of RT3 to work on a Win11 system for weeks and have been really struggling.

See if you can't manage to disable Hardware T&L. Or enable it, if it isn't.