Yes, According to Microsoft Windows 11 supported AMD processors your Athlon Gold 3150U is listed as being compatible which means it should have fTPM on it: https://docs.microsoft.com/en-us/windows-hardware/design/minimum/supported/windows-11-supported-amd-...
No it isn't activated by default. You physically need to enable it in BIOS.
To enable fTPM on your Athlon you need to enter BIOS and there should be a setting to enable fTPM on your processor probably under TPM settings or something similar.
You also need to have in BIOS UEFI Mode enabled with Secure Boot then you are all set to install Windows 11.
You can download Microsoft Win11 App to check your PC before installing the Win11 to see if everything is set for a successful installation of Windows 11.
NOTE: If in BIOS it doesn't have a BIOS setting to enable fTPM on the processor then you will need to contact your laptop Support site on how to add a TPM 2.0 device or ask them where fTPM is found in your laptop BIOS version.
You may need to update the BIOS.
Asus came out with a new BIOS version made for Windows 11 compatible as an example.