Apple Users

Yes, it does sound (ouch) like it has switched the built-in audio over to the headphone jack.

Some options on what to do ....

1) Use some software that has a volume control and see if it says "headphones" when you try and adjust the volume. E.g. my ancient iPad has a 'Videos' app that will show me it's sending audio to 'headphones' or 'ipad' depending on whether or not a headphone cable is plugged in. Even the Netflix app has something similar.

2) Use any kind of compatible plug/cable (e.g. an audio aux cable) and plug it in/out of the headphone jack a few times to try and dislodge any dust/dirt. See if the indicator from (1) changes! And/or borrow some headphones or earbuds, they're pretty cheap and common.

3) Do a real full power off and power on to fully reset the hardware/software. A normal "soft" reboot is sometimes not enough.

4) Examine the headphone jack (good light and magnifying glass) for dirt and/or corrosion. In any event, I'd use some rubbing alcohol and a small probe to clean it out even if there is no visible dirt. Google cleaning headphone jacks and/or review https://www.wikihow.com/Clean-a-Headphone-Jack

5) You could take it into an Apple Retail store. Rumor has it they have some nice cleaning tools.

In any event, I suspect the iPad is far from toast. It just needs an appropriate swift kick