no high beam or dashboard lights

I own a 94 Honda Accord EX coupe ( brought it brand new ~ 25 yrs ago ) and the car is in pretty good shape. Now the issue is that when I turn the headlight switch on ( stick switch next to the car handle) there is no dashboard lights or high beam lights ( both right & left). When I turn the switch off, the gear -position indicator lights come back but still no other dashboard lights.
I have checked all the fuses with the fuse tester and they seem OK; the high beam headlight bulbs are OK too.
I have been reading this and other forums about the issue and seems that there are few other things that could cause these light issues such as :
1) bad light relay fuse
2) bad light switch itself
3) bad dimmer switch
4) bad ground wire connections.
Would you please provide some guidance in troubleshooting for these issues ( with reference to any diagrams or videos) and how to fix it. I would greatly appreciate your kind help .

Thanks

MM