Is it possible to install a tube for a Magpul stock or maybe even Galil skeleton style stock to the M76? Since there’s no way I can find a folding tube stock, I’d like to switch out my wood stock with another type stock. I tried looking around but found nothing.

A Galil folder can be adapted to fit. There was a seller of these several years ago, but I can't recall their name. He had Galil folders that had the round stub that fit into the Galil receiver milled off. They were milled and the drilled to attach to the Valmet receiver the same way the wooden stock attached. No mods were needed on the Valmet.

Even if you could find a factory Valmet tube stock - the rear trunnion is different on the folder vs. the fixed.  I had a chance recently to buy a M76 folder for $2K and passed because I hate that design compared to the galil.  The fixed stock has a similar to regular AK type trunnion but I recall that the stock itself is in stuffed in there real good etc. so because when you remove and obviously dimensions are very different but I think good smith should be able to make something else work if you have an AK folder assembly designed for a fixed stock gun.

I don’t think I’ve ever heard anyone say they hate Valmets. Wow.

The Valmet fixed stock trunnion is very different from an AK fixed stock trunnion.After removing the single stock through-bolt from the butt plate end, the Valmet stock is easily removed.

Don't do anything that reduces the value of your investment. Nobody will pay for a Frnakensteined M76, they want it original.

IMO, there is nothing wrong with the factory hardware. Your gunsmithing adventure would be better served by converting a cheap AK into your vision.