Select the PS3UPDAT.PUP file you downloaded.
Are you trying to (e.g., "Firmware not found")?
On June 1, 2021, Sony released the PS3 Update 4.88 firmware patch. Clocking in at approximately 200MB, it wasn't a major feature overhaul but a critical maintenance patch.
Focused on system performance updates.
: The emulator became smarter at selecting necessary system modules, reducing the "manual tweaking" previously required to get games past the black screen phase. How to Install PS3 Firmware in 2021 (and beyond) To run games, RPCS3 requires the official PS3UPDAT.PUP
The RPCS3 project was incredibly active in 2021. The changelogs from the time show a constant stream of updates: