iPad os 18.6.3 constantly dropping WiFi will not connect can only use iPhone hotspot

iPadOS 18.6.3? Curious, as at the time of writing, this version does not exist - iPadOS 18.6.2 being current at this time.

If your iPad is not operating as expected, try a forced-restart - as this will often clear an isolated software issue:

Force restart iPad - Apple Support

If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset; clearly, as you are experiencing difficulties connecting to WiFi, making a fresh iCloud backup of your iPad not be viable option:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Otherwise, given you desribed circumstances, you would be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to assist with troubleshooting:

Genius Bar Reservation and Apple Support Options - Apple

I’m surprised you bothered to answer!