If you have been searching for an ultra-wide lens for the Pentax system recently, you likely will come across the $1,400 Pentax-D FA 21mm f/2.4 lens announced late last year. Whether or not you should buy it depends on how much you like Pentax.
Update 11/25/2020: Images have leaked that indicate the December 1 Livestream will include three lenses, not just one.
Sony has just released the brand new FE 20mm f/1.8 G: a lightweight, high-performance, ultra-wide prime lens for full-frame Sony mirrorless cameras that the company has dubbed "the widest full-frame prime lens in E-mount lineup."
So far, Canon has released only two ultra-fast primes for the full-frame mirrorless RF-mount system: the 50mm f/1.2 and two versions of the 85mm f/1.2. But judging by a recent patent filing, Canon has at least a couple more f/1.2 lenses in the works, and is even toying with the idea of a 18mm f/1.0.
Tamron has unveiled three much-leaked new prime lenses for full-frame Sony mirrorless cameras. The 20mm f/2.8 Di III OSD M1:2, 24mm f/2.8 Di III OSD M1:2, and 35mm f/2.8 Di III OSD M1:2 are all compact, lightweight wide-angle prime lenses that boast a 1:2 magnification ratio and very close minimum focus distances so that they can be used for every-day shooting and macro photography.