Important things to consider:
You do not need to match your Surrounds and Rears... or Atmos, for that matter, to the Front 3.
(Yes it is nice to get matching gear... but sometimes you have to roll with it, too.
)
With a rear port, you should try to avoid any flush mounting to the wall.
Something simple like this, allows you to aim and tilt the speaker a little, and keeps the port off the wall::
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This does not require any drilling into the speaker and many have used them without damaging their gear.
Hope this helps!