GDPR isn't "about tracking", it isn't even about computers, it's General data protection regulation. If your local grocer keeps a regular customer's record on paper to give you discounts, that's covered by the GDPR.
And note Part 1 section 3 points 4 and 7: "'Processing', in relation to information, means an operation or set of operations which is performed on information, or on sets of information, such as— (a)collection, recording, organisation, structuring or storage" and "“Filing system” means any structured set of personal data which is accessible according to specific criteria, whether held by automated means or manually".
See the UK Gov summary site here: https://www.gov.uk/data-protection
Or detailed law here: https://www.legislation.gov.uk/ukpga/2018/12/contents/enacte...
And note Part 1 section 3 points 4 and 7: "'Processing', in relation to information, means an operation or set of operations which is performed on information, or on sets of information, such as— (a)collection, recording, organisation, structuring or storage" and "“Filing system” means any structured set of personal data which is accessible according to specific criteria, whether held by automated means or manually".