Your device has an ID, and there are various other metrics that they can use
A demonstration:
https://coveryourtracks.eff.org/
How does tracking technology follow your trail around the web, even if you’ve taken protective measures? Cover Your Tracks shows you how trackers see your browser. It provides you with an overview of your browser’s most unique and identifying characteristics.
Is the only way to evade the ban to dodge your online fingerprint? (new phone, new email, new ph number. Etc)
Not easily. If Reddit isn't getting enough data from you, and they can't figure out who you are, they will often just ban you again