Some thoughts - this is a good overview of how stagnant the hobbyist state of the art was 20 years ago. You could probably have built all of these circuits with the those exact parts in 1973. Pretty much everything in this collection but the superhet and direct-conversion receivers is obsolete and was at best obsolescent at the time. You can think of a typical SDR as a dual-conversion receiver with a conversion stage in the digital domain. Superregens were used in remote controls right up through the turn of the century, but by the time this was written no one was designing new ones. I saw a TRF front end on a commercial ultrasound device in that era but it was not typical.

Many RF transistors are no longer available in through-hole though you can probably find small quantities for hobby projects. The msph10 is long gone. And good luck sourcing dual-gate mosfets even in smt. Infineon might still make a couple.

As a digression, it does make me think TRF receivers are probably a better learning tool than the my-second-radio regenerative receiver. Crystal radios, of course, are pure magic and it’s sad that so few people get to build them as kids.