They have a subscription model and ads which are not allowed on FDroid. FDroid also requires the software to be opensource.

This is true for the official FDroid repository but independent repo can be created [0]. This helps manage independent signing as well.

[0] : https://www.f-droid.org/en/docs/Setup_an_F-Droid_App_Repo/

FDroid do allow subscriptions and ads. They label them 'AntiFeatures' which is not as bad as it sounds; many people will still happy install the App. However FDroid to strictly insist all code is free and open source; this dose mean you are rolling your own Ad and Subscription libraries.

Correct. Newpipe on f-droid has the anti-feature of promoting a nonfree network service (YouTube) but that doesn't mean people don't install it or that it's banned from f-droid.