Any income sourced from the UK is liable to UK tax no matter where you live.
Current UK state pension is 10,400 pounds, tax allowance is 12,500 pounds.
So you get around 2,000pounds tax free from any other UK income.
20% tax will be deducted from any excess.
Best to leave your tax residence in the UK, if you don't want your financial accounts in the UK closed ..... and you want state pension rises.