Yes I did. No change. Sorry I forgot to report earlier.
I found another thread in the forum
TIDAL errors on NAS + ROCK - Support - Roon Labs Community
Which has a similarity to my problem. In my situation the TIDAL login is taking very long time and delaying the whole process. In search TIDAL is again the major blocking point.
I think we have tried whatever is possible. Somebody who knows very well the connection process and working of Roon may have a better idea. For the time being this is my roadmap:
- I will update to 1.8 and see if anything changes. If not I will accept the reality that I won’t get much help from ROON development side and return to Windows.
By the way my friend with Nucleus Plus having the same problem with a different model Linksys router has re-configured Linksys to Bridge Mode and everything is fine.
Yes I am crazy and will continue to keep my current setup. 
I have studied user manuals of some other routers available in the market and decided Asus and D-Link are quite good offering much more complicated settings to play with. Tp-Link is similar to Linksys with simple setting options. Netgear is too expensive.
How can I ask users what type of router (Brand Model)they are using if they have their own and not supplied by the service provider? The list can give a general idea which way to go for a replacement router. Although being the only device not working I would have preferred a suggestion from Roon instead of trying external remedies.
Thanks a lot Rugby for your time. Very much appreciated.
Enjoy The Music
Emre