SOLUTION:
After trying (for hours) everything here and elsewhere, nothing worked. I discovered a bizarrely specific route to re-establishing a Wi-Fi connection that fixed the issue of failing to connect to Wi-Fi.
1) Go into your router's settings
This is usually accessed via 192.168.1.1 or 192.168.0.1 from your browser
2) Navigate to your Wi-Fi name/password settings
I use a "guest network", so I had to go to that specific area of the settings
3) Change the Wi-Fi name to something else, and remove the security authentication so there is no password (it's usually a "None" option that removes the password input box).
4) After saving the changes and waiting for them to take effect, your Samsung TV should be able to connect to this newly named, open Wi-Fi network.
There shouldn't be a lock symbol next to the Wi-Fi network on your TV. If there still is, you didn't remove the security/authentication.
5) With your Wi-Fi settings page still open, change the Wi-Fi name back to it's original name and save settings
But, don't enable security/password authentication just yet.
6) Connect the TV again to this Wi-Fi network
7) Again in your Wi-Fi settings, you can now enable the password authentication, and add back the original password, and save the settings.
😎 After changes take effect, connect the TV to the network using the original Wi-Fi name and password.
This was the ONLY way to connect my TV while using the original Wi-Fi network name and password (very useful if you have multiple devices on the same network/password)
For whatever bizarre reason, if I skipped or did any of these steps out of order, the connection fails. You can't just open the network up, then close it. You have to change the name, open it, connect TV, change the name, connect TV, add password, connect TV. Very, very strange.
Anyway, I hope it works for someone else.
