Broadly speaking, there are two ways to make a broadband antenna:
1: self-similar designs
If an antenna looks the same at any scale, then it will work the same at any frequency. Examples of such antennas are the Dressler you link, but also the bowtie, spiral, fractal, and log-periodic dipole antenna designs. Practical considerations always dictate the self-similarity can't extend to infinity, but realistic designs can cover several octaves of frequency with a match good enough for reception purposes.
These designs will be best suited to the upper ranges of your 100kHz-2GHz objective, as they typically require that the lowest frequency has a wavelength on the order of the size of the antenna.
2: equally bad everywhere designs
If an antenna is small (say, less than 1/10th wavelength), it can be a bad antenna for a very wide bandwidth. The trouble is the impedance of this antenna will be very far from the typical 50 ohms, and so power transfer from from the antenna to the receiver may be so poor that it's unable to overcome the receiver noise floor.
Consequently, designs of this sort will almost always be "active", meaning there's an amplifier involved. A challenge with a wideband amplifier is overload. If you live near any commercial broadcast station it may drive the amplifier into saturation, causing harmonic distortion everywhere, rendering the antenna unusable. Some designs include filters to reject broadcast bands for this reason.
Since these antennas are electrically small, they will work best at the lower range of your 100kHz-2GHz objective.
Broadband active whips and dipoles are relatively common. A similar design can be achieved with a loop, although it's not common.
Most "small" or "magnetic" loop designs involve some capacitance at the feedpoint to make the antenna resonant at a particular frequency. Tuning the antenna this way is equivalent to putting inductance at the base of a dipole. This can very much improve the impedance match at a narrow range of frequencies, but it totally destroys the wideband characteristic.
Thus to get a truly wideband design, it's necessary to design an amplifier to work with the antenna that does not require reactive components to tune the antenna. For dipoles, this means an amplifier with a very high input impedance. For loops, a very low input impedance.
High impedance JFET amplifiers as you've found are a common design. Often, these designs will specify some JFET that's inexplicably difficult to source, and expensive if you can find it. More often than not, it's because the part is decades old. You will find designs with germanium diodes for the same reason.
Usually, these parts can be replaced with a more modern JFET. Or with some adjustment to the biasing, a MOSFET. Given that you'll likely be designing this antenna for relatively low frequencies, transistor selection is really not that critical, and just about anything can be made to work with a little engineering. Unfortunately that's a broad topic, but maybe it gives you some ideas for further questions :)
I recommend taking a look at LZ1AQ's homepage. In the articles along the left there's some great information on wideband active antennas, including some designs which look very reasonable.