Shure SM7B on a Scarlett Solo 4th Gen: is a Cloudlifter still needed?
Only just. The SM7B needs about 59 dB at speaking level and the Scarlett Solo 4th Gen publishes 57, so you are 2 dB short. Those are the published figures.
You can record the Shure SM7B on the Focusrite Scarlett Solo 4th Gen if you stay close to the capsule. The preamp is 2 dB shy of a comfortable speaking level, which is a marginal chain, not a broken one.
Shure rates the SM7B at -59.0 dBV/Pa, the voltage from a loud 94 dB tone at the grille. A speaking voice is closer to 85 dB, so the preamp still has to find about 59 dB to land near −9 dBV. That −9 dBV figure is just a tracking level: high enough to use, with space before the converter clips.
Keep a fist between your mouth and the grille, in a quiet room, and leave the gain knob near the top. A soft voice or a noisy room is when a 20 dB inline booster earns its keep: it lets you back the knob off the stop. For ordinary close speech you do not have to buy one.