This might help:
Here (Direct firmware load for rtw89/rtw8852b_fw.bin failed with error -2 · Issue #172 · lwfinger/rtw89 · GitHub) dleidert mentions that the Makefile of the driver does not install all firmware files.
My firmware folder looks incomplete: Just 8852A in there.
flieger@localhost:~> ls /lib/firmware/rtw89/
rtw8852a_fw.bin.xz