Idk which third party apps are compliant which aren’t? There is this one feg: https://f-droid.org/packages/it.belloworld.mercurygram/ Unlocks the premium app icons for free. https://f-droid.org/packages/nekox.messenger/ This one surely has a few premium features no? Unlimited accounts feg?
Personally I just use Telegramm-FOSS since years. Not sure what the actual differences to official client are at the moment, but this one is just fine and I’m never annoyed by premium feature ads like it seems to be the case for you.
I highly doubt that F-Droid team removes third party telegramm apps when they are against tos of telegramm. They are actually out there defending our freedom, even and especially when proprietary services do not want us to use Foss third party apps. Google does not want you to use third party apps for their services. F-Droid still out there publishing foss YouTube clients. Give them some credit instead of just assuming they suck up to big companies.
Honestly I thought it was an abbreviation for “for example” and probably used it one gazillion times 😅 now that I google it it seems like “e.g.” is what I was going for.