Are there any risks or disadvantages to building software from source, compared to installing a package? Can it mess with my system in any way?
I usually avoid it because I’ve found it to be a faff and often doesn’t work anyway but in a couple of cases it has been necessary.
What are the security advantages?
You can disable functionality that you don’t use or want (code that is not used cannot be exploited).
You can enable hardware/kernel specific security mitigations.
You can know what source code corresponds to the generated binary.