Hello, I'm having a problem, a big one.
To launch the game, I have to enable Secure Boot, but my motherboard simply doesn't support that mode. What should I do? Did I literally buy a brick instead of a game?

Upgrade your PC. If your system doesn't support secure boot, it is pretty old. Secure boot has existed for 14yrs! Things you can try is updating your BIOS (a newer version may have the option in it). Check your motherboard's manual, it might be an option you need to enable and it should say if it is supported. If you have a UEFI BIOS, then you "should" have secure boot ability, but not always the case. UEFI and Secure Boot go together.

Uh oh. I am
genuinely
trying to be helpful. You need to refund the game if your hardware is not TPM 2.0 & Secure Boot capable.
The above lad has made some good points. EA has released (at least on the EA BF6 forums if not here on Steam) how to check your hardware for capability and how to enable those things.
EA Forum TPM/Secure Boot Link

Uh oh. I am
genuinely
trying to be helpful. You need to refund the game if your hardware is not TPM 2.0 & Secure Boot capable.
The above lad has made some good points. EA has released (at least on the EA BF6 forums if not here on Steam) how to check your hardware for capability and how to enable those things.
EA Forum TPM/Secure Boot Link

Thanks, guys. But the problem turned out to be something else. I have a modern motherboard, but it’s a сhinese piece of ♥♥♥♥. It has a UEFI BIOS, but there’s simply no Secure Boot feature. And I won’t be able to update the BIOS either, because, again, it’s a piece of ♥♥♥♥. I really have no choice but to use a different motherboard. All the best, and thanks for your help.