This article is a bit fallacious/misleading:
I have no clue wether Boom design is vaporware or serious engineering but:
1) The initial premise, that there is a costly need to design a new engine is meta-unecessary AKA not necessarily necessary.
The article raise 2 reasons for a new engine: fuel efficiency and noise reduction.
I'd argue the concorde engine (the Rolls-Royce/Snecma Olympus 593) is excellent regarding efficiency ->
> The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.[3]

I don't know for sure what is the SOTA efficiency nowadays but IIRC last generations engines are ~10% more fuel efficient than the ones from the 80s, which where at the time behing the Rolls-royce engine hence I even doubt modern engine have better thermal efficiency than aforementioned 43%.
Regarding the topic of thermal efficiency, engines are not supposed to reach 43% without being supercritical, did Rolls-royce bypass physics laws? There must be something I ignore here. Anyway even if (?) we could design supercritical jet engines the best possible thermal efficiency would be 46-7% AKA a minor improvement.

Boom can increase fuel efficiency via the airplane architecture with e.g. composites. The near commercialisation new civil aircraft from china achieved a 10% reduction doing so.
The same can be said for noise reduction.
Hence what Boom should do is simply to order Rolls royce to produce the same engines again.
However one should know that R&D for the successor of the concorde engine has already been spent and such engine has been designed. Unfortunately the U.S imperialist oppressive bans killed the concorde economics before the production of said engine, cf: https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593....

Now about the noise levels let's adress the fact that it is a non-issue.
1) If you look at the empirical scientific comparisons, the mean noise of the concorde is significantly lower than many civil airplanes, especially the ones with 4 engines.
2) The boom while intense, is very transient. It is not heard from people inside the airplane. It is a non-problem for the obvious reason that your jet does not need to be supersonic for 100% of the trajectory, therefore a plane can and should go to very high altitude (already a supersonic requirement) and/or above low density population (rural, ocean) and only then bypass the speed of sound, making the noise boom a moot problem.
While this solution is trivial, political bans and people hysteria isn't.

What is at stakes? A lot of things, supersonics isn't just cool, it is a life saving technology that can allow the transfer of key people in records time (expert surgeon in niche disease emergency for example) which can have very high utilitaristic value. It can also make it much more pratical for key people to meet physically (e.g. key academicians for a symposium about advancing the state of the art in a topic) which is high impact considering cognitive biases regarding human agency.

Note however there are other supersonic engine makers than rolls royce, for example any country that makes supersonic military jets can obtain such engines.
It is easy to forget that the first commercial supersonic engine was not the concorde but a russian tupolev.
While the tupolev has reliability issue, few know they had an alternative engine (likely more reliable).
In addition to the tupolev engines, I would look into the state of the art https://en.wikipedia.org/wiki/Saturn_AL-31
Regarding SOTA civilian turbofan there is the https://en.wikipedia.org/wiki/Aviadvigatel_PD-14#PD-35 in development, although it can power an antonov (!) and seems very versatile I wonder if (not a turbojet) it can perform supersonicity without afterburners.

regarding those options however, russia bad, china bad.