I enabled fTPM and now my BIOS warns me "fTPM/PSP NV corrupted or structure changed". Is this ok?

Yes, if bitlocker is not on, this should be safe to do. Open Settings, type "bitlocker" into the search bar, and click on Manage Bitlocker.

If bitlocker is not enabled for any drive, you can safely proceed.

In the corner, you should see a link to "TPM Administration".

If you answer N to the firmware prompt, you will see "No TPM 1.2 compatible device found" here.

If you answer Y to the firmware prompt, you will see "Ready for use" and a bunch of TPM ownership options.

You can close this window now; it's the best way to make sure things are operating normally without actually enabling/disabling bitlocker.

Answering Y to the prompt will clear the nonvolatile structures the platform firmware has recorded for the fTPM built into AMD Ryzen processors' PSP management core (ARM Trustzone based, not the main AMD64 cores you run windows on) and they should be automatically rebuilt by the firmware as part of the defaults, including Microsoft's default certificates utilized by windows 8/10/11. As far as I know, none of this should apply to Intel based devices, as they rely on real TPM add-on-chips from Infineon and other vendors. Similar prompting may apply, without the "fTPM" nomenclature indicating a platform-embedded TPM "emulation".

For some background, the major difference between TPM 1.2, and TPM 2.0 is field-reprogrammability. TPM 2.0 is essentially software operating on a reasonably standard microcontroller chip, while 1.2 was predominantly built with logic gates and immutable. 1.2 is limited to RSA operations, while 2.0 is capable of AES and Elliptic Curve operations, as well as RSA (Which is no longer recommended).

Hope that helps.