Hi,
Please have a look at the guidance on non resident and UK investment income below regarding disregarded income.
HS300 Non-residents and investment income (2021)
UK-derived savings and investments, including UK dividends, do not qualify for split-year treatment.
The rules on disregarding these types of income from UK taxation will only apply if you are a non-UK resident shareholder for the entire tax year in which you receive the dividend income.
Thank you.