Is there a way to know if it is safe to enroll my own keys? I always wanted to, but always didn't do it, because I often read that it can make the system unbootable.
If you're using a TPM for Secure Boot, you can use the commands in https://github.com/Foxboron/sbctl/wiki/FAQ#option-rom to know for sure.
Because of this validating option ROMs is _very_ important to a point some would argue it's more important then validating that e.g. your Linux kernel has not been modified
Honestly option ROMs IMHO should not exist in the way they do (for security reasons), but they outdate secure boot by quite a bit and like many of this "old legacy features a lot of things depend on" are just really hard to get right of.
Through without question the design this ended up with has a terrible UX.
But most laptops with a reasonable EFI implementation and no dedicated graphics card do luckily not have option ROMs (through their firmware update tool might have something similar, but you can just not use it).
Most option ROMs are signed by the same set of Microsoft keys, You can make sure to enroll this keys alongside your custom platform key (e.g. the tool sbctl can do so for you). While this does tend to work it has one drawback which is if someone has that key they can break your secure boot chain, i.e. it weakens the benefits custom platform keys give you.
Option ROMs signed by vendor keys are somewhat rare, but sometimes (parts of) firmware update tools are signed by vendor keys, in which case you can choose between not updating your firmware, disabling secure boot while doing so or hoping you can find the (pub)keys for the keys they used somewhere on the internet.
In the end you probably want to see if someone already tried it and had success.