I think that these days, there is a lot less interest in the electronics hobby than there used to be. Electronic products have become so miniaturized and cheap due to off-shore automated manufacturing (and low-cost labor), that they have become opaque objects about which we are less curious. If you take them apart, there is not much to see or hack into, and good luck getting a schematic. These days, "maker" projects like robotics and 3-D printing are more likely to capture the attention cycles of young people. But I have noticed an uptick in interest on the DIY Audio forums - people are identifying themselves as "noobs" and asking for guidance in getting started in the hobby.

While the hobby can be rewarding, it can also be frustrating and costly. It requires patience and perseverance. In the "good old days" we had Heathkits, Knight Kits, EICO kits, etc. and you got a box full of everything needed to complete the project, so it was almost instant gratification. Plus, especially in the case of Heathkits, you learned a lot if you read the manual (not just the assembly instructions) because they explained the theory of how it worked in plain English, what all the components were, and how to measure and test it. That is mostly gone now, so it is a little harder to get going. One exception is Elekit in Japan. They make a few tube amp kits which are reportedly very well done. Another example is Akitika; they provide well-documented kits for solid-state amplifiers, preamps and also have upgrades for the old Dynaco tube kits under their Updatemydynaco.com brand. They have received some good reviews and are reasonably priced. Another kit provider is Transcendent. They have been around since the 1990s and specialize in tube preamps and OTL tube power amps. Another source of kits (solid-state) is Neurochrome.

Aside from those kit providers, at the starting level, usually, the best you can hope for these days is a ready-made PCB (Printed Circuit Board) and a BOM (Bill Of Materials). You then need to order all the parts from the BOM and wait for them to trickle in. There are often no assembly instructions so you need to carefully follow the schematic and PCB and match up the parts with where they go on the PCB. You also need to know how to correctly identify the polarity and orientation of components where it matters, and this requires referring to data sheets - keep those browser tabs open on your computer! In the case of the DIY Audio forums, there are some excellent build guides that have been generously contributed by members, notably "6L6". And when you run into issues there are lots of "helpers" in the forums who can offer advice.

If you are less ambitious and want to build something more quickly, there are many pre-assembled modules available at low cost, mostly from China. Many of these are clones of classic circuits and you can get your own enclosure and power supply and build up from there. Many of these are available on Amazon and AliExpress.

If you are more ambitious and want to start from scratch, you need to breadboard your circuits (which can be fun in itself), experiment with modifications to your design, finalize it, then design your own PCB and get it fabricated, then obtain the parts, then put it all together and hope for no magic smoke. It becomes a one-person project management journey.

My advice - plan all this out beforehand and allocate the time and money so you don't get discouraged and abandon the project. Do the research, seek out some expert advice, and don't be surprised when you hit an obstacle. My own experience has been that projects always take longer than I expect, so I have learned to pace myself and work in small chunks of effort. If I take a couple of days to stuff and solder a PCB, that's fine. Work in short "sprints" so you don't burn out. Taking your time also results in fewer mistakes (and mistakes WILL happen).