Ryzen 3600 CPU's do have an fTPM that's 2.0 compatible, so you are good to go there.
I've noticed that oddness with my BIOS too (TUF B550m Plus/5800X) ...that is, it has a UEFI+Legacy setting and it reported it was in UEFI mode with Secure Boot enabled. I'm not sure what it meant, but I flipped it to UEFI mode only with no issues encountered.
You said you only just installed Windows11, so I assume the OS is "pristine" and new, so to speak. If so, now's the time to switch everything on so first is to enable Secure Boot, but do not mess with custom keys. Then also turn on the fTPM...it may be called a "security processor" in BIOS settings, that's the case with mine. If the OS refuses to start you can reset CMOS, even re-install Win11 if you need to since it's fresh. So not much lost.
BTW: from within Windows, go into the Device Security systems settings (type it in the Search box). You're looking to see if you have the Security Processor and Secure Boot enabled at least. You might also need to enable SVM in BIOS: that's Secure Virtual Mode which allows apps to create secure virtual machines. It can create problems with other apps so I leave it disabled unless it's needed.