It's very easy to get confused with what's going on with audio and the different jack connectors and the signals they are carrying.  The terminology can trip you up.  What you refer to as a 'stereo' jack I would likely call a TRS jack (Tip-Ring-Sleeve).  This jack could be carrying 2 channels (usually stereo) of unbalanced audio, or it could be carrying one channel of balanced audio at line level or microphone level,

A 'Mono' jack I would call a TS jack (Tip-Sleeve), and this will only carry one channel of unbalanced audio - but this could be mic level for a crappy karaoke system, line level for all manner of stuff, or loudspeaker level, which if incorrectly connected to the input stage of a mixer would likely cause damage.  I have also seen TS  and TRS jacks used for remote buttons and indicators for smoke machines and there is no audio involved there!

Then you get 4-pole TRRS jacks used for headsets on phones and laptops which carry left and right unbalanced audio to the headphones, and unbalanced audio from the microphone!

Thankfully applications for power amplifiers with a 'stereo' (2-channel) output on a single TRS jack that would suffer badly from a short circuit with a TS jack inserted are rare.  Headphone amps being an exception but their outputs are much lower and if well designed will have short circuit protection.  Also thankfully, as others have said, most 'line level' audio outputs are quite resilient these days and they need to be otherwise they wouldn't last long!

It's very easy to get confused with what's going on with audio and the different jack connectors and the signals they are carrying.  The terminology can trip you up.  What you refer to as a 'stereo' jack I would likely call a TRS jack (Tip-Ring-Sleeve).  This jack could be carrying 2 channels (usually stereo) of unbalanced audio, or it could be carrying one channel of balanced audio at line level or microphone level,

A 'Mono' jack I would call a TS jack (Tip-Sleeve), and this will only carry one channel of unbalanced audio - but this could be mic level for a crappy karaoke system, line level for all manner of stuff, or loudspeaker level, which if incorrectly connected to the input stage of a mixer would likely cause damage.  I have also seen TS  and TRS jacks used for remote buttons and indicators for smoke machines and there is no audio involved there!

Then you get 4-pole TRRS jacks used for headsets on phones and laptops which carry left and right unbalanced audio to the headphones, and unbalanced audio from the microphone!

Thankfully applications for power amplifiers with a 'stereo' (2-channel) output on a single TRS jack that would suffer badly from a short circuit with a TS jack inserted are rare.  Headphone amps being an exception but their outputs are much lower and if well designed will have short circuit protection.  Also thankfully, as others have said, most 'line level' audio outputs are quite resilient these days and they need to be otherwise they wouldn't last long!