I have to think that it would be pretty hard to fool a TPM "user". But there are physical TPM modules and TPM that are executed in firmware, or an fTPM, like AMD and Intel do with CPU's and UEFI since 2017 or so. I've even read there is a software TPM2.0, but no clue as to whether Win11 install will accept it. But it seems to me it would be useless if using BitLocker since you have to decrypt the drive very early (TPM stores the keys for decryption) to start the OS so it can run the software.
If you're concerned that your system isn't going to get Win11 because it's hasn't got either a hardware TPM or firmware TPM 2.0 I wouldn't let it bother you. First is that if it's that old then it will probably not comply on any of several other...