From all the analytical data I've seen, aside from fentanyl, the majority of those pressed 30's have some acetaminophen, many contain metamizole for some weird reason, and also a significant proportion contain unreacted ANPP (a precursor used to nake fentanyl). In terms of actives some contain a variety of both fentanyl and fentanyl analogs (more recently 4-fluorofentanyl or 4-fluoroisobutyrylfentanyl). In rare cases they might contain synth noids, benzos and anything else they feel like including. Some have been found to actually contain heroin itself though almost certainly trace amounts. In general however the active opioid is fentanyl or a fentanyl analog, or both.
I have no interest in taking these pills, I simply like to read forensic/analytical results just out of curiosity, I do a few times a week.
The real danger with these pressed 30s is not so much getting a pill with some poisonous adulturant, it's getting a pill with a toxic dose of fentanyl or fentanyl analogs. Some of the pills have been found to have something like 11-12mg of fentanyl equivalent, which is clearly a manufacturing error, but it is one that could result in death for many typical users. Yet even aside from the chance of getting a "hot" pill, the average fentanyl content seems to be creeping up over time, which can make the average pressed 30 quite dangerous for non-tolerant users.