Is it possible to Install big packages directly on usb without doing extroot?
How are you going to access them ?
wget http://downloads.openwrt.org……….apk
apk extract *.apk --destination /mnt/sda
seems to work
That's why I'm asking! 
is it possible to install adguard home on usb and use that or like how I always do it make the firmware file with adguardhome in it it compresses it down and I'm left with 15 mib usable storage on my rbr50v1