Will Apple have to change CE to UKCA on the first of January? Or not? To be honest, I can't be bothered to even start reading the rules to work it out.
Using the UKCA mark from 1 January 2021
The UKCA marking can be used from 1 January 2021. However, to allow businesses time to adjust to the new requirements, you will still be able to use the CE marking until 1 January 2022 in most cases.
In some cases you will need to apply the new UKCA marking to goods being sold in Great Britain immediately from 1 January 2021. You are encouraged to be ready to use the UKCA marking as soon as possible before this date.
https://www.gov.uk/guidance/using-the-ukca-mark-from-1-january-2021