Will disabling secure boot prevent any OSes already installed from booting?? Would i have to reinstall?? I got music production software that would not play nicely with reinstall due to licenses.
FUD, fear, uncertainty and doubt, one of the most powerful weapons in the M$ arsenal...
But that's also the reason M$ insists on TPMs, and using BitLocker on normal Windows 11 installs, to complete the dependence, which doesn't
need to exist.
Disabling secure boot on a Windows system that doesn't use BitLocker doesn't prevent Windows being able to boot, unless it doesn't
want to. In any case you should be able to disable secure boot in the BIOS, and simply test it... unless disabling secure boot were to involve deleting a stored master key to access your data, you can always just re-enable it.
Of course there is no telling if there are programmed nasties and I suggest you don't try that on a managed corporate laptop.
I avoid using media encryption, especially TPM based, because all my Windows machines are dual or triple boot, I often move or copy my media including operating systems between machines (including VMs) and because I like the ability to operate on file systems and media across operating systems, e.g. NTFS on Linux.
Secure boot in my understanding mostly prevents UEFI booting off files or media that's not cryptographically signed and that's why enabling secure boot may make Linux or older Windows installations inaccessible. Disabling it shouldn't be destructive, just cause a dependency when a media encryption key won't be made available without it.
But since I've worked hard to avoid it for many years, I can't give you certainty. I only know that in my installations, there is no functional difference between enabling and disabling it at any moment (just did a BIOS update yesterday, which always tends to reset it to 'secure').
But my Windows 11 IoT LTSC also runs with all TPMs disabled in the BIOS before installation as well as a setting to disable BitLocker installation from the start.
Before I had my IoT LTSC variant all figured out, I was able to remove BitLocker from a system, where Microsoft had managed to sneak in this new default: you just need to do that
before you disable the TPU, swap the CPU or do other 'harm' to the security of your PC.