From my tests with an random medium site it isn't possible. The site has set the A-record to the medium ip addresses. ublock origin uses the detection of cname records. For filtering my search records i use ublacklist.

in uBlock Origin preferences, -> My Filters -> add:

    ||medium.com^

That should block their site and all the sub-domain custom domains that point to it. [0]

As for blocking domains that point to it without using "medium.com" in the name, that would likely be a never-ending process of whack-a-mole, I think. They use CloudFlare and blocking CF's CIDR blocks [1] can certainly be done but then much of the websites on the internet would be blocked.

[0] - https://www.netify.ai/resources/domains/medium.com

[1] - https://bgp.he.net/AS13335#_prefixes