First some definitions and concepts. Then some simple
experiments.
Your are confusing earth ground with something called safety
ground. Your TV has no safety ground connection because a
third ground inside the TV is isolated - a floating ground. A
voltage difference between a floating ground and safety ground
is undefined. It may or may not harm you if you touch both
simultaneously.
In the meantime, anything conductive outside of that TV must
be galvanically isolated from floating ground. Isolated does
not mean no electrical conductivity. Isolated means minimal
electrical connection.
Two tests for sufficient human safety. First, plug the TV
into a working (and pre-tested) GFCI outlet. Connect a jumper
cable from that audio ground to the safety ground (ie a screw
holding the wall receptacle cover plate). This test should
not trip the GFCI. Some current will pass from that audio
ground into wall receptacle. Current must be so low as to not
trip GFCI.
Second, measure that leakage current using the meter set for
AC current. Measure well less than 150 microamps (0.15
milliamps) from audio ground to wall receptacle 'safety
ground'. Some leakage current should be measured. Current so
low as to not threaten human life and not trip the GFCI.
Galvanic isolation does not mean zero current. It means
minimal leakage current.
BTW, the safety ground on wall receptacle does nothing for
lightning protection. Wall receptacle does not provide an
earthing ground for so many reasons. The safety ground wire is
too long (well over 10 feet), has too many splices, has too
many sharp bends, is bundled with other non-earthing wires,
etc. Earthing is not found at a wall receptacle for so many
above reasons and due to excessive wire impedance. Earthing
for lightning protection means a short wire directly to single
point earth ground; which is different from safety ground,
floating ground, audio ground, and motherboard ground inside a
computer. Don't confuse these many grounds even though some
may be interconnected.