I have no doubt that this has been asked before, but I searched and couldn't find anything. I currently run a Lowrance HDS12 Gen 3 at the console as well as the Humminbird 998c that came in the dash which I use solely for navigation. Saw a bargain on a Garmin 93sv so I grabbed it and a panoptix/livescope transducer to add livescope to the front of the boat and replace the Humminbird that originally came on the boat. Took it to a nearby installer to have it installed and was told they wouldn't do it because I "couldn't run multiple brands of fishfinders on the boat at one time because the transducers would interfere with one-another and I would never receive a clear picture and then I would come back to them mad because what they installed wasn't working."

So is it possible to run an HDS12 Gen3 at the console with a transom-mounted totalscan transducer and a 93sv with Livescope at the front of the boat at the same time without issue or would I be better off swapping the HDS12 out for a 12" Garmin?

As long as the transducers are operating on different frequencies then it shouldn't be a problem at all.

I have a friend who runs a Helix 12 gen 1 at the console/transducer at the stern, and a Garmin Livescope at the bow. No issues

Not a well informed installer.

SE Kansas grass grower (retired)

Garmin has done an excellent job with there units. We have yet to get any interference out of Garmin when teamed up with other brands. Nor do the other brand see any issues.
Of course, your units operation is as good as your installation.

I’ve got a Lowrance Elite TI at the console and a Hook 2 on the trolling motor. I’ve got a Garmin 93sv with Livescope on a poleducer a couple of feet away from the Hook 2. I run all 3 at the same time regularly with no interference.

What tmd said.