It's not exactly correct to say that the games like Caligula or Monark are "by ex-Atlus staffers". They're there more as mentors rather than true driving force behind them. Check the interview with the Caligula director, "Den Faminico Gamer interview with The Caligula Effect producer Takuya Yamanaka", on Digi-Lab blog. Caligula is a very low budget, and was intentionally made to appeal to very specific type of people, not mainstream. Satomi helped him turn his ideas into an actual game story.
Ah, you know, the truth is that i mostly blocked these games out of my mind because I knew I'd never play them myself and instead compartmentalized them as by "ex-Atlus staff" just as a memory shorthand. Let's review a few, since they're generally going to be eligible for Digital Devil Spawn:
Has nothing to do with any Atlus staff whatsoever.
Oh, this is the one that's a brazen Persona ripoff
That's probably why I got my wires crossed about it.
Streaming Knowledge will be taking a look at this fine gamesoft tomorrow!
I often have trouble remembering this game's name
This one's filthy with old Atlus guys like Ryotaro Ito, Kazunari Suzuki, and Tsukasa Masuko
Caligula [Effect] {Overdose} (2016,2017) {2018,2019}
Hm, so the sequel to this is apparently okay, and the nomenclature is a little confusing, but the "Overdose" version is somehow a "remake" of the Vita original (the original release just seems like it was incomplete more than anything)
Written by Tadashi Satomi, music by Tsukasa Masuko
I feel like there's maybe one more (that's not like Guns Undarkness or Jewel Summoner), but it's not coming to mind.