Updating this, because no method was posted, and because clearing cache many times and praying for your device to come up after every restart gets old really fast.
Also, most methods searchable online do not work with the latest Magisk version, because as soon as it sees an installed Magisk version older than the app it automatically forces itself to go online and install the new app - the old method of downgrading the app via install channel and then downgrading Magisk does not work since v25.1.
Step by step:
1. Download:
https://github.com/topjohnwu/Magisk/releases/download/v25.2/Magisk-v25.2.apk and rename the file from .apk to .zip in file manager.
2. Open magisk app, go to modules and select "remove" on all modules.
3. Still in the modules screen, select "Install from storage" and install the Magisk-v25.2.zip file.
4. Reboot.
5. Rename the Magisk-v25.2.zip back to .apk.
6. Uninstall the magisk app from applications. Just hold on the icon and select uninstall, do not use the uninstall option inside the app.
7. Install Magisk-v25.2.apk, now you got your app back to the old version as well.
8. Open the app, which is now 25.2 and go to Settings in upper right corner. Under "App" change "Update Channel" to "Custom" and enter this URL:
https://raw.githubusercontent.com/t...26c0454a947cb4fa0a3bb1bc7d29e7caa/stable.json
Done. You are now on 25.2 and it won't ask you to upgrade ever again.
Enjoy simple things in life, such as rebooting your phone. Or starting it again after it runs out of battery without doing a voodoo dance.
