Extensions Guidelines & Policies | Twitch Developers details the guidelines that all extensions must follow. No one here can give a definitive answer on if something will/wont pass review as it’s entirely up to the review team and your specific submission.
From what people have tried in the past though, anything involving mining crypto, or facilitating exchanging crypto within the Extension, or directing users off-site to exchange crypto, has been completely denied. If you was to simply display text of a crypto wallet that users may send tips to, that may or may not be allowed and you’d have to go through review, but if the user gets anything in return for crypto such as getting to access features or do things in-extension in return for that exchange it’ll likely be denied.