Opening this thread to add some details of my experience so far with the product and its setup - on 5GHz WiFi network in particular.
In short, the the hardware of SYMFONISK Bookshelf Gen2 appears to support only the lower frequency channels of the 5 GHz WiFi spectrum, which is a bummer.
I use the TP-Link Omada setup and have enabled the AI based WiFi band optimization to run once a week (which enabled it to function much more efficiently and I have never had any problem with it on my other devices); after one such run is when the device fell off the network and could not connect back. However it continued to funciton normally the moment I enabled 2.4 GHz network with the same SSID.
Post reaching out to Sonos support - to arrive at no conclusion, resetting my Sonos device once and going through all the logs on my network end, I figured out that the device does not support higher frequency channels such as 149, 157, etc.
The moment I manually changes the settings to a lower frequence channel - 36 / 40 / 52 / etc, the device works like a charm, with no hiccups or isses what so ever.
Therefore, whoever is facing challenges with Ikea based Sonos devices on 5 GHz WiFi, make sure to check what channel is your device using for 5GHz broadcast.
Hope this helps somebody! 