The OnePlus smartphone's personal Wi-Fi hotspot can be configured with its own network name and a password that you set yourself to prevent unauthorized third-party access.
It does not matter what your own hotspot is called or whether the password consists only of numbers or letters in upper and lower case.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  Wi-Fi & network
Step 3:  Tap on  Hotspot & tethering
Step 4:  Tap on  Wi-Fi hotspot
Step 5:  Tap on  Hotspot name
Step 6:  Enter the  Hotspot name  and tap  OK
Step 7:  Tap on  Hotspot password
Step 8:  Enter the  Hotspot password  and tap  OK
  1. Open the Settings
  2. Tap on Wi-Fi & network
  3. Tap on Hotspot & tethering
  4. Tap on Wi-Fi hotspot
  5. Tap on Hotspot name
  6. Enter the Hotspot name and tap OK
  7. Tap on Hotspot password
  8. Enter the Hotspot password and tap OK

OnePlus Instructions