I am also not against f-droid having apps that might require payment (like nextcloud or etesync), but I do think that new anti-feature (perhaps too strong a word, but it is how they are called currently) for apps which are crippled (eg. have some features disabled) until user pays probably should be implemented.
Or alternatively (or in addition) at the beginning of the description, have a paragraph which makes it easily visible and transparent what you get by default, and for what you must pay or have some other restriction. (currently in for example FairMail, there is only ambiguous “pro features” buried in the middle of the long description)
For example, for FairMail it might say at the beginning of the description “Note: Some of the features of this software are DISABLED unless you pay for them.”
Or for nextcloud and etesync it might say “Note: This software requires that you either HOST your own instance, or PAY to use commercial instance” (EteSync does say it - but even there, IMHO it should be as a first, separate paragraph; instead in a middle of non-formatted blob of description)
(It would also be good is wording could be standardized, so all software with same requirements could spell it out the same way)
I think that does not require technical changes (just editing the descriptions0, would not be disrespectful toward developers, and most importantly would be transparent and clear and concise to users what they should expect.
Also, instead of “Pro features” (which could be interpreted by some to mean that you could install the software and start using some advanced/professional features) in description could we please write “Features requiring payment” ? It would be much less misleading that way (at least for some of us non-native english speakers).