Wall electrical box cutter - GIF

[BuffaloJohn]

You can get one of these to fit your oscillating multitool - see:

https://jonard.com/ebc-electrical-wall-outlet-cutters

or for those who have a HF near you (since this is instore only):

https://www.harborfreight.com/electr...ols-56666.html

and of course, there are a bunch of these on Amazon as well, with ratings from poor to not so poor.

An interesting comment that I saw, probably repeated often:

"too short and wide for most 1-gang and 2-gang old work boxes"