How best to isolate dirty power caused air conditioners or other motor driven devices at the dirty device itself?

I have two air conditioners that are the source of some voltage fluctuation/line noise in my home. The two A/C’s running at the same time is definitely and unambiguously at fault. This is primarily a problem because it causes LED lights to flicker.

Rewiring/adding circuits is not an option, nor is disassembly or modification of the A/C’s themselves.

I would like to isolate the A/C’s with something that plugs in inline to keep the rest of the power clean. I’d prefer to stick something between the A/C’s and the wall (because there are only two of them) than have to put lots of filters/conditioners on everything else.

My Google-Fu has failed me – I can only seem to find information on how to protect sensitive devices from EMI/voltage fluctuations (e.g. stick a online UPS between a computer and the wall), and not how to properly mitigate a known dirty device.

I’m in the US with 120VAC single phase power.

What is the proper device to add inline to an air conditioner or other motor-driven device in order to keep the rest of the power clean? Isolation transformer? Line conditioner? UPS (if so, what flavor – battery backup in an outage doesn’t matter except as a means to smooth the inrush voltage fluctuations)? Massive ferrite bead?

Edit:

I have read several proscriptions against using a UPS or AVR, etc on electric motors, primarily because the startup current draw of the motor might exceed the capabilities of the device. (See almost every post on laser printers for reference) Most advice seems to treat this as a blanket prohibition, but in reality there is obviously more nuance to it: https://www.apc.com/us/en/faqs/FA158851/
So to refine the question somewhat – assuming the inline device is properly sized for the motor and providing a natural sinewave, as noted in the APC link above, what is the proper device to use to isolate/smooth a motor driven appliance from its 120V AC power supply?