The LEGO® MINDSTORMS® Robot Inventor kit (LEGO set 51515) was released by LEGO in 2020, and LEGO has announced its retirement at the end of 2022. After this time, it may still be available while stocks still last, or new or used from various resellers, such as Amazon.
LEGO also offers a similar kit called Spike Prime, which uses the same hub, motor, and sensor electronics (in different colors), but the building parts inventory and programming software are both different, so the 51515 projects on this site will not be directly compatible.
The VEX® IQ (1st gen) Super Kit was sold by Innovation First under the VEX Robotics brand from 2012 to 2022. This kit is called the 1st generation of VEX IQ, and is no longer available for sale from VEX, as it has been replaced by the 2nd generation kit below.
The 1st and 2nd generation kits are largely compatible overall (although the electronics and building parts selection are both different), and they use the same VEXcode programming software used by projects on this site, so projects for one kit may be adaptable to the other kit with some changes.
The VEX® IQ (2nd gen) Education Kit was introduced in 2022 and is sold by Innovation First under the VEX Robotics brand. This kit is called the 2nd generation of VEX IQ, and contains upgraded electronics and a different building parts selection compared to the 1st generation kit above.
The 1st and 2nd generation Vex IQ kits are similar overall, and they both use the same VEXcode programming software used by projects on this site, so projects for one kit may be adaptable to the other kit with some changes. See this article for a comparison of the two.