I am not sure how to read notes with noteheads that look like a double-sharp (see the image below for an example). So far, I have dicovered that this notehead might be called "ornate X notehead" and can be found in the SMuFL specification.
At first, I thought this might be another style of writing ghost notes (usually with a simple X as notehead). However an arrangement of "Sweet Home Alabama" in one of my songbooks contains such ghost notes with a simple X as notehead while the chorus has these ornate X noteheads. So the latter cannot also stand for ghost notes. By the way, alongside standard notation the songbook contains tabulatur where these noteheads appear too, without a stem of course. So, how do you play these notes on guitar?
Update: Adding examples from the songbook as requested in comments. First image shows the use of use of convential x-noteheads for muted notes in the intro. Second image shows the ornate x noteheads in the chorus.