You asked
Samyang af 24mm f 1 8 fe vs viltrox af 24mm f 1 8?
These two are very close on paper. Both are 24mm f/1.8 primes for full frame, both have autofocus, and neither is stabilised. On APS-C they frame like 36mm and give about the depth of field of f/2.7.
The real difference is the mount. The Samyang AF 24mm f/1.8 FE is listed for Sony E only. The Viltrox AF 24mm f/1.8 also fits Nikon Z. If you shoot Nikon Z, Viltrox is the one for you. If you shoot Sony E, check your body on each page's camera list and choose on price and availability. Samyang's page notes it is often bought for night-sky work, but the site doesn't say the two differ in that way, so don't assume one is better for it.
Before you buy, read third-party lenses on the lenses page to confirm your camera supports this kind of lens.
Written by Claude from this site's pages.