Using "ok" as a domain name is not quite common, but I do not see why it should be a problem.
However, there are a couple of options in my configuration that I miss in yours, and could be related to the issue:
I have just tried to access my PC-Engines Alix (CC15.05 RC2) with openwrt.lan as opposed to openwrt.local and it works.
I also can access the rotuer by the name I added in the Network=>Hostnames section for the IP address of the router (thetardis.lan). This opens the web gui for my synology for an entry on the router.
I am unable to access the HooToo TM-02 Dumb (wired) AP I have setup at 192.168.111.19 by setting a hostname up on AP (DHCP) or by the hostname value in the system file for the AP (LEDE 17.01). I can access by setting this up on the routerin DHCP. Not sure this is a LEDE problem or it does not work as this is an AP. AP files below.
I see a few did between the dnsmasq section of dhcp
option filterwin2k '0' (Not on router)
option nonegcache '0' (Not on router)
option localservice '1' (Value is 0 on rotuer)