LENR, is it plausible?

I am going to guess maybe not.  Not that I am an expert.  Call me an armchair type of guy who tends to spout off on subjects with not enough training to be an authority.  But, I'll try to back it up with some info that supports my view.

As I wrote before, it seems doubtful that LENR theory, according to Widom Larsen, explains nickel hydrogen systems.  If the E-cat works, it will be a cold fusion device, not a LENR device.

Widom Larsen requires the absorption of neutrons- thus it needs a neutron source and a likely candidate for absorption.  Also, when the absorption occurs, it should have a short half life, so that the energy will be released soon so that it can be useful.  If it takes years, and doesn't yield all that much energy, it won't do you much good.   For example, let's look at iron.  Here's virtual all of the isotopes of iron in nature:

As you can see from this table, this just about covers all of the iron that you'll find

2nd column from left is concentration in nature, this represents over 99% of iron isotopes

 You'll also want to note the second from the right column and compare that to the right column.  If the number in the second column is bigger than the right most column, it is not likely to absorb a neutron.  Since 28 is much bigger than 1.28, it doesn't seem to be an inviting target for neutrons.

Now, in Fe54, those two numbers are about equal, an absorption seems possible.  But if it occurs, it has a half life of over 2 years.  And the energy release seen below is not impressive:

So, I think you may want to rule out iron and hydrogen too.  I covered nickel previously.  One possibility may be vanadium.  I'll check that in a future post.