Sorry, I was trying to save space, but I can see how only starting the quote in the middle of the paragraph is misleading. I edited the quote to include the context.
For me this reads as them explaining and condemning that dilemma, instead of considering it as an option for F-Droid.
IMO, it read more like acknowledging concerns around ads but not explicitly condemning it. But I'm not going to form an opinion about it until they do something, or at least make their intentions clearer.
ads in Firefox
That's a common misconception. For users like myself who use uBlock Origin, Firefox supporting PPA changes nothing at all (as pointed out by the Firefox CTO). The only users who would see an ad that uses PPA are users who would otherwise see ads that use tracking.
That is why the EFF supports it.
If they were talking about Privacy-Preserving Attribution like Firefox is experimenting with supporting on MDN, that would be one thing, but it doesn't sound like that's what F-Droid is talking about.
Not only are privacy and data protection founding principles for both Mobifree and F-Droid, the use of tracking-based in-app advertising poses a moral dilemma as well. If someone wants to gain access to an app, but does not have the financial means to purchase it, they can use it at a different kind of price - their user data.
F-Droid is also considering ads that contain no tracking, which removes that moral dillema, IMO:
It should be mentioned that it is possible to include in-app advertising without user tracking. However the lead conversion ratio drops dramatically, so the efficacy of this approach is not nearly as high.
That's basically what PPA is, advertising without tracking. If advertisers want to pay for it, then great.
Edit: Downvoting without responding like 
If you were trying to do a mention, it broke
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Again, it's not advertising, it's a form of privacy protection. There are no ads in Firefox, and they did not add any mechanism for tracking users, so calling it browser advertising is advertising your own technology illiteracy.