I can only view my skin from the inventory menu,
I'm using Aristois client, and I'd like to have the Skin-Swapper mod in my modslist to change my skin client side.
If any more info is needed please reply back.

Same issue on all skin swapper versions. Someone find a fix? We are still waiting for this.From what I can see,most people with this bug also have sodium,lithium,starlight installed.Removing all the mods except skin swapper fixes this issue.

The best solution I would suggest is to enable "2d" skin viewing in the config. That should at least hold you over until I implement a proper fix.

Update: Actually,people that are using Wildfire's gender mod breaks skin swapper,if you are using it,remove it and it will work.If you are not using it tho and you are still having this issue,try removing mods,one by one until you find the mod that breaks skin swapper.Also try to use offline mode to see if that works.

I am experiencing the same issue launching from both CurseForge and MultiMC.
I don't have Sodium etc installed, nor do I have Optifine.
F3+T doesn't do anything, and it even makes hitboxes with F3+B invisible, and hides the block breaking texture animation. Really weird stuff.

After some rather rigorous testing, removing one mod at a time, I have determined that in my specific case, it's Not Enough Animations that causes the issues.
I am using v3.1.2 Skin Swapper for 1.19 and v1.6.1 NEA for 1.19

As soon as I remove NEA, the 3D preview in the Skin Swapping screen works, and swapping skins doesn't result in any invisible entities/textures/whatevers.
That being said, if I choose 2D in the mod settings, it doesn't conflict.