how can i get a diagnostic and system check/repair virtually via mac?

Advice? ..to inquire directly, ask, & see what they say:

• Get Support - https://getsupport.apple.com/

Hi seamus114,

It's not possible to get a remote hardware repair; that will need to be done in person. You can schedule a hardware repair by contacting Apple Support.

You can, however, check your Mac's hardware for issues. Follow these steps:

On an Intel-based Mac: Hold down the D key as you power on or restart your Mac. Release the key when a spinning globe appears, or when you're prompted to select a language. If that doesn't work, try holding down Option-D instead.

On a Mac with Apple silicon: Shut down your Mac, then press and hold the power button until your Mac starts loading Startup Options. When the boot picker appears, hold down Command-D until your Mac restarts.

Anything like what you recommended to Seamus and his MBP for ipad?

Can you please link the thread you're referring to?

EDIT: Just realized you were referring to this thread.

For iPad, you'll need to take it in to an Apple Store or an Apple Authorized Service Provider. iOS and iPadOS do indeed have a system diagnostics app, but that can only be revealed/summoned by Apple or authorized personnel.