You can apply for naturalisation one year after you are granted indefinite leave to remain. If they had a passport in 2019, this person must have applied for IL

You can apply for naturalisation one year after you are granted indefinite leave to remain. If they had a passport in 2019, this person must have applied for ILR before the EU Settlement Scheme, which started in 2019. So in order to prove they lived in the UK, they must have sent kilograms of payslips (2-3 per year), reference letters, various proofs of address (2-3 per year) and a list of all travels abroad (to prove you haven’t been outside of the UK for more that 6 months), which you can’t do if you are in prison abroad. It took me 2-3 weeks to collect all the documentation, and I never changed address and I only worked for blue chip companies. My partner could not apply for ILR before the settlement scheme because half the companies she worked for went out of business and couldn’t provide reference letters. He may have been very lucky with his case worker, but this is definitely not the “tip of the iceberg” of anything. You don’t need to be a British citizen to claim benefits or furlough money or public funds. An ILR or having worked for X months should suffice (assuming you can live in the UK on 150£ per week).