The only way to be positive regards any of the following would be to contact the Federal Benefits Unit at the London Embassy:
https://uk.usembassy.gov/u-s-citizen-services/federal-benefits/Having said that, US SSA benefits for a non-USC spouse (are/were) possible. I am very familiar with the situation, but I now find all the information on the SSA site is no longer accessible. I don't know if things have changed recently but the
US UK Totalization Agreement is still in place. It is the guarantor of the right for a UK resident spouse to claim SSA benefits and survivors benefits from the UK.
https://www.ssa.gov/international/Agreement_Texts/uk.htmlThe primary SSA retirement beneficiaryFirst, the SSA must have affirmed an individual is an SSA qualified retirement benefit recipient. In other words, someone with 40+ quarters of SSA qualified contributions. That person must be entitled to (receiving) an SSA retirement benefit.
The non-USC spouse The UK, non-USC, spouse may not apply for a spousal SSA benefit until the primary SSA beneficiary is in receipt of the SSA retirement benefit, and must meet the SSA age requirements for receiving a benefit. They apply directly to the FBU at the London embassy. The spousal SSA benefit will be 1/2 of the primary beneficiaries benefit amount,
provided it is taken at full retirement age (66.5). If the spouse is below FRA when applying, the benefit will be reduced in line with normal for SSA practice. The non-USC spouse may never have lived, worked, or even set foot in the US, but they are still entitled to the SSA benefit.
WEPThe primary SSA beneficiary may have had their SSA entitlement reduced by WEP. The spousal pension will be 1/2 of the WEPed benefit amount if taken at FRA. If taken earlier, it will be 1/2 the WEPed amount plus the normal reduction for an early benefit on the WEPed amount.
The spousal benefitIt may be paid in the UK as is normal practice to the spouse's UK bank account, monthly. It will increase (%) yearly if a COLA award is made by the SSA to SSA retirement benefits. The spouse will be issued with a
'not allowed to work in the USA' social security number and card. They will also be issued a Medicare Part A card.
UK taxThe spouse must file a Self Assessment tax return with HMRC, on the 'Foreign pages', claiming the gross amount of payment made by the SSA during the UK tax year.
US taxThe spouse, if not a US person, will not have to file a US tax return (unless they file as MFJ with a US Person). No US tax is withheld from the SSA benefit. A 1099-R will be issued yearly to both the IRS and the recipient, but SSA retirement benefits are not taxed by the US if the individual is resident in the UK, under the US UK Treaty.
https://www.crevelingandcreveling.com/blog/what-expat-americans-foreign-spouses-need-know-about-social-security