Fun fact: iOS's "40 seconds per ringtone" limitation is a complete and utter lie.
Want to bypass it on iOS 14? Super easy!
1. Jailbreak your iDevice of choice.
2. Install Filza. You do not need to activate it.
3. Grab a clip shorter than 40 seconds, convert it to m4r, and place it on your iDevice with iTunes. In iTunes, rename it to what you want the final ringtone to be, NOT what it is currently. This is your "dummy file".
4. Grab your ringtone file that is longer than 40 seconds and convert it to m4r.
5. Place it on your iDevice with Filza's WebDAV server option in /var/mobile/iTunes_Control/Ringtones.
6. In Filza on your iDevice, navigate to /var/mobile/iTunes_Control/Ringtones.
7. Find your dummy file by playing all the files in the Ringtones folder. It will be named a random string of 4 letters.
8. Delete the dummy file.
9. Rename your ringtone file to the string of 4 letters that your dummy file was named.
10. You are done!