As of Writing I have CrossStitch running on a Velocity connected Fabric 1.21.4 server with various other mods running. Before using CrossStitch, I could not get Velocity to work on the server, with previously mentioned mods. As far as I can tell it works pretty flawlessly, but it took me forever to find this, and when I did it I initially didn't try it due to seeing that it "didn't support 1.21.4". The same issue seems to be reflected on the Curseforge page. Cross Stitch also does appear when searching "proxy" filtered to fabric, but not when you filter to 1.21.4, which means that it is definitely discoverable, just not for 1.21.4.
As of Writing I have CrossStitch running on a Velocity connected Fabric 1.21.4 server with various other mods running. Before using CrossStitch, I could not get Velocity to work on the server, with previously mentioned mods. As far as I can tell it works pretty flawlessly, but it took me forever to find this, and when I did it I initially didn't try it due to seeing that it "didn't support 1.21.4". The same issue seems to be reflected on the Curseforge page. Cross Stitch also does appear when searching "proxy" filtered to fabric, but not when you filter to 1.21.4, which means that it is definitely discoverable, just not for 1.21.4.