Apologies if this has been answered already, I have tried searching the forum but couldn't find a similar topic

I am trying to find a way for my unmarried partner to stay in the country after his current visa expires. The problem is we've only been a couple for approx 1 year and 4 months, and are not married. We have been sharing financials (joint account) and living together for the past year.
He is a non-EEA citizen in the UK on a Tier 5 visa which expires on 11th of September and can't be extended (he is 30 years old). At that point he will be in the UK for 10 years, however he does not yet qualify for PR as there was a period of 1 year which he spent abroad studying (exceeding allowed absence quota in 10 year period).
I am an EU citizen, and have also obtained British citizenship in June this year.
When his current visa expires we will be together for less than 2 years, which makes me believe we don't qualify for any the family visa options.
Are we missing something? I would assume there would be a path for somebody in our situation to be able to stay together in the UK, without being forced to either get married or leave, but I can't find one.
We are looking at EEA Residence Card or EU family settlement scheme (which, for unmarried couples, requires RC or Family Permit as well) options, but are there maybe any other paths which would be more appropriate

Has anybody ever been successful with an unmarried partner application as a partner of less than 2 years? I am also thinking if we have better chance of applying for a specific type of a family visa, are some family visas more flexible than others perhaps?
We don't mind trying for an RC, as I understand until the application gets answered he can stay in the country based on his expired Tier 5 visa. However I am not sure what happens if/when we get rejected on the count of not being a couple for long enough - can we apply again for a different family visa, or does he have to leave immediately?

I am baffled, seems like we're in this weird gap which isn't covered anywhere... or maybe we're just missing something. Any pointers will be greatly appreciated!
Thank you all in advance.