Hi GNUser
 ... The new rtw88 driver seems hardwired to look for firmware inside /lib/firmware/rtw88. ... 
I don't think so. I ran this against the TC16 kernel source package:
grep -rs "lib\/firmware" Kernel16.x/linux-6.12.11/*There wasn't a  "usr/local"  to be found anywhere.
I ran the same search against the TC10 kernel source with the same results.
The kernel config files don't list a firmware directory either.
I did find this in /lib/udev/firmware.sh:
FIRMWARE_DIRS="/lib/firmware /usr/local/lib/firmware"/lib/udev/firmware.sh gets called by /etc/udev/rules.d/50-firmware.rules.
I think these 2 files are used to load firmware from extensions.
Are you loading  firmware-rtlwifi.tcz  before  wireless-KERNEL.tcz?