@inna I think you're looking at this the wrong way.
Tubes sound the way they do because of the distortion they make. If you can make something else to make distortion of the same kind it will sound the same for that reason.
There are lots of things out there you can loosely call 'transistors'. Some are meant for linear operation and some are meant for switching. No-one these days would take germanium transistors seriously except for repairing some old thing. These days GANFETs have lots of buzz around them. Amps that use them have garnered a lot of praise. But in ten years or so there will likely be something else that is better. Maybe someday people will laugh when GANFETs are mentioned. All that you really need to do when looking into this sort of thing is seeing if the manufacturer made some effort to sidestep obsolescence. If class D, is the module easily replaced? If yes, it might not matter if GANFETs are obsolete.
Tubes are fun to play with because they are so simple. But from a designer's point of view, they come with lots of limitations. Right now is an interesting time in audio history; class D has taken over everything but high end audio. Its making inroads there too but its taken about 50 years to be taken seriously. IME once you get an amp to play and sound like real music, you stop caring about whether it glows in the dark.