It's kind of strange for me that the most secure out of the box wifi router I could find was made in China by a Hong Kong based company. The new one comes with 2 2.5 slots fwiw.
Yeah I don't trust the firmware they come with. It's some customised variant of OpenWRT, but I replace it with vanilla immediately. At least this is very easy (simply upload the new firmware in the web interface, no serial port or TFTP shenanigans necessary).
FWIW I don't trust the OEM firmware of any router. They're all a mix of crap, some intentional, some not.