Solo Lead Belay Device of Choice: GriGri+
GriGri’s are the ubiquitous belay device of choice for any serious sport (read: redpoint) climber. This universal usage makes it the world's most tested belay device, catching falls at all angles, with cross loaded biners, with significant brake slack, and so on. Failure reports are rare, and the failure modes can be managed for LRS usage. (Though again, we are significantly misusing the device)
The same benefits of a GriGri while belaying someone “working a route” come in handy while climbing solo, too. It is relatively easy to yard up the rope after a fall (or add a PCP and winch style ascend if hanging in space). One can work moves, clip up, and generally project routes like normal. There is also risk reduction in being able to immediately lower at the top of the pitch without switching devices. Derek and I have both taken hundreds of falls LRS with this system, some quite large.
Slack for clipping is fed downward through the GriGri, prior to making the clip. A learned motion that comes natural in time. Making a high-clip generally requires 3-5 pumps of rope. It is helpful to count them when climbing hard so you don’t come up short! It’s better to feed out too much slack than to short rope yourself when trying hard. After making a high-clip, one must resist the urge to cinch tight through the GriGri which can cause short, abrupt falls.
The GriGri+ specifically has the benefit of TR Mode: its lower spring preload on the cam causes locking sensitivity to increase. This is great for LRS peace of mind! A chest harness or bungee must orient the GriGri upwards for TR Mode to auto-feed at all - feeding downward then works very smoothly to pull slack, but the device is very grabby when the climber strand is pulled upwards (the direction of a LRS regular fall or take). This allows very skinny ropes to be used without concern of slippage, but check the mode dial before every pitch. A modern Generation of the standard GriGri works okay too, but be cognizant of rope diameter selection for a reliable catch with the stiffer cam spring.
See this video to help visualize the sensitivity required for a no-hands engagement. This failure mode is greatly reduced by GriGri+'s TR Mode: The Physics of GriGri | When does No-Hands Belay Fail?
If you climb LRS style often, consider having a dedicated GriGri+ to maintain a fresh cam surface. The steel cam bump that pinches the rope does wear out from lowering and rappelling. A fresh and dedicated device is a great idea to avoid slippage and longer-than-expected falls.
*Aid Climbing Risk: The GriGri has a downfall for aid soloing - if one is standing in an aid ladder on a piece that is also clipped through the lead rope, and the piece falls, weighting the ladder midair during a fall could hold the GriGri cam down This may prevent cam engagement. This can be prevented by not clipping the rope to a piece of gear until standing in ladders on the next piece.