Currently, Calyx OS is only supporting the Xiaomi Mi A2 and any Google Pixel device newer than the Pixel 2. The Calyx team have also stated that they will be supporting select OnePlus devices as early as 2024.
If you are attempting to install Calyx on your device, make sure that it is compatible with the devices Calyx can operate on. It is important that you download the client that is designed for the model of phone that you have.
Other mobile device manufacturers like Samsung, LG, and Motorola will often prevent you from unlocking the bootloader, which is the feature that ultimately allows you to install open-source operating systems such as Calyx.
For more information regarding device support, please reference the official CalyxOS support page. https://calyxos.org/docs/guide/device-support/