Here's a fun one:
- I keep getting a weird error on my phone, and the only thing I can really understand from tapping around on the details is that it says something about "Let's Encrypt". What did you do to my phone?
I don't know enough about the smartphone ecosystem to know if this is only one specific brand or if the UI is better in newer versions, but it certainly causes confusion when like, someone's mail system certificate expired or there's some malware on the device that has a back-end with a bad certificate, so every time the device checks mail or whatever(regardless of what the user is trying to do in the meantime) one sees an error. This has definitely caused confusion on the forum when the community tries to help fix the server that's involved when the user doesn't actually know anything about the server. See Let's Encrypt got on my iphone without permission, Help Pop Up Message, Newbie trying to understand for some example threads where there was a lot of confusion.
In general ensuring there's at least some part of the FAQ that makes sense to end-users, rather than web site developers/administrators, would probably make sense.