Filter use G1x Mark lll

Peter Bendheim wrote:

Thanks again, and I've commented in great detail below, hopefully, you'll have something to add to that.

As far as the original G1X is concerned you had to buy a lousy plastic adaptor.

Seeing your comment about the M series, I use a UV filter on the 22mm lens and I have since day one without issue. The G1x lens part seems pretty similar to me conceptually?

I am an absolute fan of high quality Hoya Pro1 HD (99.35% light transmission) & Multi Coated (97%+ light transmission) UV filters - which were recently designed especially for digital cameras with CMOS sensors on ALL of my lenses. There is but ONE exception and that's the EF-M 22mm f/2 STM lens. I don't bother putting a filter on that lens to protect it.  The optics on that lens are so tiny that they are protected from knocks and scratches entirely by the front portion of the lens barrel. In the event where I might be shooting in an environment where salt air is a problem, I might consider a filter on the day but I'd be more likely to use a Circular Polarizer than a UV filter near ocean views.  The lens is also cheap enough that I would rather buy a new one that have it repaired.
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I found it necessary to clean my 22mm lens just once and it was a very easy chore. Just be sure to dampen the cloth with the isopropyl alcohol (or whatever you use) and don't dab the bottle directly against the lens... or you'll get liquid inside the lens assembly. I still carry it with the lens cap on because an indirect stray ray of sunlight can cook the sensor on a mirrorless camera even if the camera is turned off. I had to do that with the original G1X as well. And I always used a UV filter with the G1X. The higher end UV filters allow virtually all the light through whilst adding a layer of protection to the camera's not-so-easy-to-fix lens.
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One thing I've noticed is that whenever I've had a problem with a lens on a PowerShot, it took about 4 to 6 weeks to get the camera back from Canon and it ALWAYS had optical problems afterwards. Always. Soft corners, distortions, soft center at certain focal lengths. It's almost always just GREAT straight out of the box but as soon as you send something to Canon for repair, there's issues afterwards.  I can't confidently say that I've been happy with anything they've sent back and if you return it to them they don't always fix the problem you send it in for.
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Canon no longer do their own Repairs here in Australia. They have "Authorized Service Centers" now and those are run by local bidders. It's always worth protecting your lenses just so you're not without a camera while it's being serviced or repaired.
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The plastic Filter Mount ring on the original G1X was made of a composite material - which made it very hard and not at all brittle. The only tricky thing was using both palms of your hands to loosen the mount from any filter that got stuck... without touching the filter surfaces.