How is that defined? For many businesses it is essential to know conversion rates and which users buy, especially if they invest in ads so they can calculate their ROI and know if their campaigns bring in profit or loss, which I think it's pretty "essential".
The law doesn't say anything about it, though: this is just the interpretation and how courts have been treating it, so I wouldn't try to find loopholes around the word "essential" if you intent to follow it.
A court has ruled that tracking cookies used by ad networks, analytics and retargeting require consent [1].
Nothing stopping you from analysing your logged-user data, though (as long as you disclose it to your customers and comply with the rest of GDPR), so it's possible to have those kinds of measurements even without those stupid cookie banners.
[1] https://techcrunch.com/2019/10/01/europes-top-court-says-act...
[1] https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...
Your citation does not mention URLs or clarify why they might be non-essential.
If you're using it to display a page (say: React Router), then it's essential functionality.
If you're using the URL to propagate a unique hash between pages that is used to identify the user for marketing purposes, then it requires consent.
The ePrivacy is just a _directive_ and doesn't oblige to anything. It's the local laws of Europe that do. We have compiled a detailed list of all the European countries and the respective laws that require an analytics service for opt-in or opt-out style banner. [2]
Retention is not possible without cookies or localStorage, but you can measure retention without storing or processing any PII information.
[1] https://volument.com [2] https://volument.com/learn/data-privacy