I'm in a same sex relationship with my girlfriend for almost 6 years now. We lived in Portugal for the past 3 years and I have my residency there approved by work. She's Portuguese/Brazilian and have already her pre settlement status approved in the UK.
I arrived in the UK on Dec 27th 2020 and applied for the pre settlement status on that same day as unmarried partner, since we were not able to make a civil partnership/marriage before. Unfortunately, I did not have Family Permit, once I arrived in the UK, and today, May 19th, I got my decision saying that I got my application refused based on no family permit.

"The required evidence of family relationship for a durable partner of a relevant EEA
citizen is a valid family permit or residence card issued under the EEA Regulations (or by
the Bailiwick of Jersey, the Bailiwick of Guernsey or the Isle of Man) as the durable
partner of that EEA citizen and, where the applicant does not have a documented right of
permanent residence, evidence which satisfies the Secretary of State that the durable
partnership continues to subsist.
Home Office records do not show that you have been issued with a family permit or
residence card under the EEA Regulations as the durable partner of the EEA national and
you have not provided a relevant document issued on this basis by any of the Islands."
Above is the reason for refusal that they stated.. I understand that I was apparently supposed to have the Family Permit, but upon some research I could see that this requirement for the family permit is a bit confuse, since I have been with my partner for several years and we have several evidences that we've been together, including rent agreement that states our both names for house we lived in Brazil..
Does anyone have any idea on the best way to appeal on this one?

Thanks!
