No cellphone can eliminate tracking by association. For years you go to work driving the same roads or taking the same bus along with people with their cellphones, associating with the same towers and hotspots and stopping by at the same shop to buy a newspaper. Then one day you buy a PinePhone or a Purism phone with a new SIM thinking they'll lose all your tracks. Well, no. If you bring your phone along for enough time, it will do the same things the former one did, so that a simple query asking for new phone numbers producing the same metadata will return your new number along with some new others, which can be easily filtered away by conditioning the search to those associating for example with a tower where you usually spend holidays, or almost identical tower connections with a phone close to yours (wife, for example).

Cellphones such as the PinePhone or the Librem aren't intended to hide that you are you; that will be discovered in hours anyway and it's not even worth attempting; they're rather intended as a way to avoid direct data access and surveillance by corporations and governments. That is, they will immediately know it's you and where you are with coarse accuracy, but what you are up to is another story: they need to access the data directly by sneaking malicious software into your phone, which its Open Source nature will made extremely difficult to achieve.

You do one self-identifying thing (from the PoV of the mobile network operator) on your phone over network and your IMEI is forever tainted with your identity from then on.

(Say someone or some corp sends you a two-factor SMS that includes some identifying data)

Purism doesn't have this solved either.

And from the PoV of governement surveillance, lol. Just forget using a PSTN.