To resolve the SameSite Cookie issue, we highly recommend to upgrade your Magento 2 to the latest release.
For users running Chrome 80 and higher, Chrome is enforcing a secure-by-default cookie classification system, treating cookies that have no declared SameSite value as SameSite=Lax cookies. Only cookies set as SameSite=None; Secure will be available in third-party contexts, provided they’re being accessed from secure connections.
Note: SameSite field isn’t yet widely supported in older browsers, as well as Safari and Firefox.
After noticing our merchants were experiencing issues, we immediately flagged it with Magento in their GitHub issue. Magento let us know they expect some changes from Adyen’s side, which our developers have released. Magento will also provide the possibility for developers to configure the SameSite Cookie type for each cookie variable (to be added in a future Magento release).
If you want to test your solution but you can't see the warnings, enable the experimental flags (chrome://flags), and set all the SameSite functions to Enabled.