Acoustic ceiling for reducing reverberation

but a normally furnished living room serves the purpose at a fraction of the price

I actually have a hall problem during conversations in a room measuring 4x4m, built from porous bricks, fairly small window (240x100) and normally furnished with carpet. I have the felt panels and they really work well. Visually, however, it feels a bit unsettling because of all the stripes. Now I'm considering whether to hang a Ligno panel on the wall as decoration. I don't find it pretty.

Suspended ceiling with drywall perforated panels.

My son has fitted 8cm thick stone wool with a frame and covered it with fabric so that it does not fall out of the frame. DIY perfect solution but very much work.

Nevertheless, I would prefer to tackle the problem instead of solving it with software.
Does anyone have experience with the products from "ligno"?

No experience yet, but our architect has good experience with it and we will probably do it that way too, though it will still take a few years...
One more note about the software: with acoustics, it's not just about listening to music, but especially about feeling comfortable in the room, without music. And acoustics have a major influence on that, which cannot be corrected by software.

In principle, the Lignotrend acoustic panels are not (much) different from the felt wood stuff - with Ligno, the acoustic absorber is the wood fiber. Basically, the Lignotrend solution is better - and you can also simulate the effects much more thoroughly because the manufacturer provides all acoustic data in detail (DIY store panels usually come with a rather uninformative "sound absorption class").

However, they don't work miracles either - if your (theoretical) problem really has acoustic absorption as a solution, then you also have to provide sufficient cavities behind it, as well as probably additional backing (e.g. hemp or PE fleece). But even then, you won't be able to solve everything below 300 Hz with it.

if your (theoretical) problem really has acoustic absorption as a solution, then you must also provide sufficient cavities behind it,

Sure, the killed sound also needs a cemetery ;-)