Do you really need cookies for this or could you also use your server logs for this?
Per default you could not gather statistics but ask inside you app if people are willing to participate in making the app better and if they would agree to accept some cookies for this reason.
I don't need cookies for this. However, AFAIK the GDPR doesn't just apply to cookies, it applies to any data retention, or at least anything that could be tied to an IP address or a certain user.
Maybe the key is to have stats that are purely anonymous, eg, how many people visited this page.
If you're using server logs, without any cookies or other client-side storage, then the ePrivacy Directive is not relevant and you're thinking about the GDPR. Unlike ePrivacy, the GDPR is specifically concerned with personal data, so if you are careful in how you set up your logs you can generally still collect good analytics on how people use your site without accidentally collecting data on how a specific person uses your site.
Per default you could not gather statistics but ask inside you app if people are willing to participate in making the app better and if they would agree to accept some cookies for this reason.