Did you apply for and get any form of documentation about your residence in the UK, either a Residence Certificate or a Document certifying Permanent Residence, before 2020? They would have been a blue coloured tri-fold card.
You could try
applying for Settled Status when you are back in the UK (it is a free application), but it is highly likely to fail given that you have been absent from the UK for three years (Permanent Residence under the pre-Brexit EEA Regulations/EU Directive would have lapsed automatically after any single absence for more than two years).
If you do get Settled Status, which, as
alterhase58 mentioned above is a requirement to apply for British citizenship, you won't qualify to apply to naturalise as a British citizen for a few years.
To start with, you need to have held ILR/Settled Status for at least one year before the date of naturalisation application.
To add to that, there are absences and physical presence conditions counting back from the date of naturalisation application have to be met.
For instance, if I applied for naturalisation today, I would have to prove that
(a) I had ILR/Settled Status before 08/04/2023,
(b) I was physically present in the UK on 09/04/2019 (five years before today)
(c) I was not absent from the UK for more than 450 days outside the UK between the date in (b) and today.
Having lived in the UK for any five years in the past is not enough. It needs to be the five years immediately before the date of naturalisation application.
So, to summarise
(a) You can apply for Settled Status, but you are highly likely to be refused.
(b) If you do get Settled Status, it will be a few (at least three+) years before you become eligible to apply to naturalise as a British citizenship.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.