You can keep your existing IF-ISA's open and will still get UK tax relief on money and investments held in it.
Pertaining to applying for a Kuflink IF-ISA, you must confirm that you are a resident in the United Kingdom for tax purposes or, if not so resident, either perform duties which, by virtue of Section 28 of Income Tax (Earnings & Pensions) Act 2003 (Crown employees serving overseas), are treated as being performed in the United Kingdom, or you are married to or in a civil partnership with, a person who performs such duties. You must inform Kuflink if you cease to be so resident or to perform such duties or be married to, or in a civil partnership with, a person who performs such duties.
If you are no longer a resident of the UK for TAX purposes, you can no longer add any further money to your IF-ISA or open a new IF-ISA.
However, you can keep your existing IF-ISA's open and will still get UK tax relief on money and investments held in it. You can transfer an IF-ISA to another provider even if you are not a resident in the UK. You can pay into the Kuflink IF-ISA again when you return and become a UK resident.
When you are no longer a resident, then you may be subject to the tax regime of the country you are now resident in and may have to pay tax on UK ISA's. Please seek independent financial advice.