I noticed that virtual cursor doesn't work on my Fabric Fabulously Optimized 1.19.4 instance.
So I tried to set up clean instance with minimal mods and reproduced the behavior without problems.
I've used Steam Deck to reproduce the issue, don't think it matters but worth noting.

I have set up a fresh 0.19.4 instance using Prism Launcher with Fabric Loader 0.14.21.
Added only bare minimum Fabric API 0.84.0, Framework (Fabric) 0.6.4 and Controllable (Fabric) 0.19.2.

After launching the newly created instance, the controller is detected and working.
Left stick should show and move virtual cursor but the virtual cursor isn't visible on the screen.
The virtual cursor style option (Light, Dark, Console, Legacy) doesn't matter, cursor is not visible for any selection.
The cursor is still selecting menu items so it is there, just not drawn on screen.

PS. MC 1.20.1. with Fabric API 0.84.0, Framework (Fabric) 0.6.5 and Controllable (Fabric) 0.20.2 is working OK.

Other people are also having this issue on fabric

had this too, what fixed it for me was using using fabric api version 0.80.0, tested with older versions too and it worked but version after 0.80.0 didnt work