How smart connect work? I'm using DIR-882, when i enable my smart connect. my phone will took more than 15 seconds to connect to WiFi, can see that the phone connect, and disconnect few times before connect to the WiFi.

<<Background>>
I suspect the free Wi-Fi6 router comes with Unifi upgrade a bit crappy. Recent months i noticed my phone sometime will auto switch between 5Ghz and 2.4Ghz, and if I forget one of the SSID, it will drop the Wi-Fi connection and switch to Data. Similar problem happens to my TV that if i exit YouTube and join back, it showing gray screen and it take about 15mins to connect back, TV Setting shows connected but no internet.

Speedtest using UniFi apps shows 290+ Mbps download and 40+ upload, but i noticed my YouTube (On all devices) will sometime drop to 144P before change back to 360~720P.

I wanted to switch back my Old D-Link AC2600, but not sure where did my mum keep it
<</End of Background>>

Previously i bought AC2600 (end of 2018) due to it wide coverage as my house is Terrace intermediate that is extra Long and the modem is located at the first room which nearest to the front and Kitchen is the further back (Can't install in center as the ONT is in the room).

Now i wonder if any Sifu here can recommend similar router? but with Wi-fi 6/6E/7 that doesn't break my wallet.

Budget <500
House Estimated Size: Lebih Kurang 3000 Sqft , about 40m in length. 6-7m width