Do you install door frames before or after applying drywall plaster?

Drywall first

You must install the drywall first and then fit the door frames into the openings afterward. Pre-hung door frames are designed to wrap flush over the thickness of finished drywall sheets; putting frames in first would cause the drywall to push against them, warping the wood jambs. Drywalling first also allows you to mud and sand the openings cleanly without gouging your new door frames, while the decorative casing trim you install at the end will completely hide any rough drywall edges.

Typically, the door frame or pre-hung door is installed before drywall finishing and painting. The usual sequence is framing, door installation, drywall installation, taping and mudding, followed by trim and final finishing. Installing the door frame first allows the drywall to be fitted neatly to the frame and helps ensure proper alignment and consistent gaps around the opening. If you're using only a jamb and casing rather than a pre-hung unit, there can be some variation in the order depending on the project, but in most residential renovations the door frame goes in before the drywall is finished. — Ainger Group Roofing and Exteriors

Install door frames after the drywall. Installing to door frame first will most likely lead to damage of the frame from sanding and mudding.

The drywall should be done done first so you can do the door trims on top of the drywall

Install the door frame (jamb) first, then hang the drywall up to the frame. After that, tape, mud, sand, and paint the drywall. Finally, install the door casing/trim. This gives the cleanest finish and ensures the opening is square and properly aligned.