LGeeRemote barely functions based on the reviews. It was originally designed without WebOS, WebOS was added, then updated. No reviews or updates in a year means it may no longer work.
Smartify seems similar to the LGeeRemote app, though started later. It might still work since it was updated within the last year.
LG TV Plus should have worked if the model is in the supported list (it should be based on age). The serial number you show is not the serial number for the TV, it is for the sticker. The model number would be more useful. WebOS should have an about section to tell you the model, and possibly the WiFi connection it is using. You may also find that there are WebOS updates for the TV too.
One of the reviews from the Smartify app may have the answer for you. Most modern routers have 2 bands 2.4GHz used by WiFi B and N devices and 5.0GHz used by WiFi G and N devices. If is possible that the TV is using 2.4 GHz and the iPad is using 5 GHz (or vice versa) possibly making the connection not work.
If you can see both networks, try switching the connection on the TV (If the router is close to the TV) to 5GHz, or move the iPad to the 2.4GHz (If the router is behind several walls from the TV) to see if that resolves the issue.
Your Google search was not going to help since the iPad isn't linked yet. A better term would have been iPad connect LG Smart TV which has several articles with advice like ensuring they are on the same network and app recommendations and help for those apps.
Since this is more of an LG problem, not an iOS problem, this is all the help I will provide here.