GIMP Version: 2.10.24
Operating System: Windows
OS Version: 10
GIMP Experience: Intermediate Level
plug-ins or scripts: G'MIC 2.9.7

Recently, one of the filters in G'MIC stopped working--anisotropic smoothing. Unfortunately, it's one I use a lot. When I try to run it, it completes instantly having done 0%. Other G'MIC filters still work.

I've tried uninstalling and reinstalling G'MIC. Still broken.

I've tried uninstalling and reinstalling Gimp and G'MIC. Still broken.

I've tried uninstalling and reinstalling G'MIC 3.0.2. Still broken.

I really need anisotropic smoothing! It's one of the things I use a lot to get beveled fonts to look good. What else can I do? Thanks.

Works fine here in G'mic 3.0.1 using Repair > Smooth [anisotropic].

I'm sorry; I don't follow.

Are you saying I need to use version 3.0.1?

Or are you pointing at where to find it in the G'MIC menu? I've been using anisotropic smoothing for a while. I know where it is. It's that I press apply and nothing happens.

Similar to racer-x, using linux and it is easier for me to swap gmic_gimp_qt versions. Anisotropic smoothing working for both gmic 2.9.7 and 3.0.2

Switching to Win10 and Gimp 2.10.30 and gmic 3.0.2 Anisotropic working here as well. Start looking at something in your installation.
I would disable your gmic profile where all the settings are held, C:\Users\"yourname"\AppData\Roaming\gmic - rename to (say) gmic-bak.

Start Gimp up, gmic makes a new default profile. Is Anisotropic smoothing working ?

I stated menu location to help others find it so they could test also. I too am running Linux. BTW, there are two filters for anisotropic when you search for it.