iPhone11 no longer connects to home wifi even though the check mark indicates I am on the network. After backup and complete wipe, I was able to restore for only 30 min when it reverted back to "LTE" only.

If you have enabled WiFi Assist and have no internet** then it will switch to Cellular.

** Connecting to Wifi is the first part and then getting connected to the Internet is the second

1. If you connect to Wifi, doesn't necessarily mean you are connected to the internet. If you are not connected to wifi could be a problem with iPhone settings or Router/Modem Settings
2. If you are not connected to the internet is the sole issue of Router / Modem Settings. Contact your ISP immediately