I’m planning to apply to Columbia, but I’m really worried because my test dates keep getting pushed out/cancelled. I know that even the Ivies are going test-optional, but with schools this competitive, scores can really help. I’m frustrated because I’ve spent so long studying and taking practice tests, but it will all mean nothing if colleges can’t see that. Does anyone know how much this would affect me? Columbia is my dream school so I’m really concerned.
Columbia, like the other Ivies (and most, if not all T20s,) is test-optional, so it will not hurt your application if you are unable to take the SAT or ACT. However, test scores are one way in which Columbia and other selective colleges assess your academic strength: so if you are unable to submit an SAT/ACT score, they will look to your GPA/course rigor, AP/IB/SAT Subject Test scores (if you have them, these are a great way to show strength in a subject area, especially your intended major) etc. for evidence that you’ll be able to handle their coursework.
Once Admissions is certain of this, they’ll look to the remainder of your application (essays, letters, extracurricular activities etc.) for evidence that you’ve thoroughly researched your “fit” with Columbia and will take advantage of the resources of Columbia and NYC in-order to pursue your career goals and passions to become a future alumni that they’re proud of. 
Columbia’s Undergraduate Admissions website provides some helpful information about their testing requirements and how it fits into their holistic review process: https://undergrad.admissions.columbia.edu/content/revised-testing-policy-2020-2021
Hope that helps! Good luck with admissions!
@Georts Our take on the same problem (7 cancellations total!) is to find a HS that actually has in-person classes now. I don’t know if this is an option in your area. Reach further than it would be reasonable under any other circumstances if you need to. A rural location triples your chances of the test happening.
For us, it required a 2-hr drive to the one neighboring state, 1 time zone east of us for SAT on 8/29 (so a night in a motel was necessary), and another 1.5-hr drive to another state, in the same time zone, so we left at 5:50 am, with D sleeping in the back seat most of the way, for the ACT on 9/12. It may seem a bit extreme but in both schools, the parking lot looked like an intestate rest area - license plates from all over the region, except the cars were quite a bit more upscale than in a typical rest area 
Both exams went very smoothly.
One more thing: are you sure no standardized tests are planned in your school? In many states it is a graduation requirement so even with the remote learning, they invite their own students for the exam (in our case, SAT will be administered at school on 9/23).
Anyway, good luck with your plans, and I won’t repeat the CC mantra about getting all your bases covered, you know that already