Wanted to understand if there is a concept of a truly decentralised fiat, with no government control, but collated to real world. It's high time such a currency comes to fruition, specially with CBDC's etc.

Is there is any project going on to build it ?
Such is very counter intuitive. Hope you Google the different meanings of the Word "fiat" then compare that to the ideals of decentralized currency like Bitcoin.
Fiat and truly
Decentralized currency are contradictory. It should never be used together to mean truly decentralized due mainly to the fact that the first truly decentralized currency like Bitcoin is a voluntary currency system with participants who can join or leave the system at will.
Maybe
Decentralized National currency will work, rather than
Decentralized Forced/imposed Currency.Bitcoin could be called the currency of the free. The other is mostly for slaves.