The Instructions to Form 5227 state "filer" and don't define the word (albeit that may have been somewhat obvious to the drafter of the instructions).  We relied on the word "trust" in the regs (and as you noted above).  They could have made the instructions more clear.  That said, I don't believe many of the entities filing Form 5227 have 'operations' giving rise to the extensive filings of information returns, other than, perhaps, the K-1(s).

I'm convinced that Intuit is unable to assemble all the supporting schedules needed to electronically file Form 5227 since many of them come from the other form sets (i.e., 1040, 1041, 990, etc.).  Even the ability to file an extension for Form 5227 would be helpful but apparently not possible from either the 1041 or 990 package.  Curious if anyone has been able to use/override the Form 8868 in either of those packages and actually efile an extension.  We simply weren't willing to take the chance.