The trusted boot is explained for windows because it is fully implemented by Microsoft.
If you'd like to read about trusted boot on Ubuntu here there is an Ubuntu official wiki page that explains pretty good the steps.
About your questions advantages/disadvantages, it is a dilemma in my personal opinion....
Trusted boot is about enabling security at hardware/firmware level and not software level, which is a security countermeasure to avoid malware load before the operating system(s).
Said that, in the other end, by enabling security boot you are basically putting your system in the hand of Microsoft. Today Microsoft supports trusted boot for a number of Linux distros and it doesn't include custom Linux distros but Linux Foundation has implemented a generic loader signed by Microsoft that will allow any Linux to load, read this link from Linux foundation.
The problem is, this is always signed by Microsoft, in simple words there are two disadvantages:
- Microsoft is not a community such as Linux, it is a capital gain company and if it loses its interest towards Linux it can cut it out at any time.
- You are losing your freedom
The history will tell by itself that there will be never a good relationship between companies like Microsoft and communities such as Free Open Source Software.
I hope this will help you understand.
Thanks