This is what in my opinion is reasonable,the rest sounds as bullshit even though I wonder whether a university may ask a charlatan to hold a conference

First of all matter is not a scientific term let's say mass instead
There are two interpretation of the Einstein's equation which are known as the weak and the strong claim

Einstein wrote
M = L / C^2
Where L is the kinetic energy only
He did not write
E = M * C^2
where E is a generic form of energy

in both cases M is the rest mass

From a math wiewpoint it is the same stuff but from a physical viewpoint it is not
Einstein assumed, at least at the beginning , that if a body absorbs or emits kinetic energy then absorbs loses mass but he did not exclude that a body may have a residual mass regardless of the content of energy
This is the weak claim

The latter equation is the modern form
In this interpretation the whole rest mass can be turned into energy
This is the strong claim which is accepted by most scientists but not all

An other controversial topic is : is a radiation also matter ?

let's assume that matter is a synonimous with mass
This is what Newton thought

Matter annihilation , by definition, means that an entity having a rest mass such as electron or proton turn into entitity which dont have a rest mass i,e a photon
However photons have also dynamic properties similar to material particles
Scientists say that photons do not have mass but they have a momentum

If the answer to the above question is : yes a radiation is a form of matter then this guy is right
By the way many scientits disagree with this claim but it is not a bullshit