Actually the GDPR definition of personal data is very wide, a bit to wide in my opinion (one of the reasons GDPR is not always taken serious) but that is a different topic.

IANAL but the way I read it is that any data that can be linked with you as a natural person could be considered personal data.

Therefore if LinkedIn is saving a log in a database similar to: "profile x viewed person y" and profile y has your name that would qualify as personal data in my view.

https://gdpr.eu/eu-gdpr-personal-data/

Especially interesting is the section "Personal data and the purpose for processing" since LinkedIn is selling access to the data of who viewed your profile the perspective of if it is or is not personal data may be shifted.