I am developing a flutter desktop app (which later may support mobile), which allows users to login into their MS account so that I can retrieve profile information.

Currently I open the MS login URL in the default web browser. After acquiring the access token via redirect to my web server I wanted to pass that access token via deep linking (custom URL scheme) back to my flutter app. The problem I face is, that the access token is longer than 2000 chars, but some web browsers only support ~2000 chars.

How could I solve this problem?

If possible I want to avoid using the ms graph package, as I want to support different platforms such as Slack as well and using the upper approach would work for all.