The process is now to make a donation of at least 6€ https://ko-fi.com/tolriq then send me your trial ID by PM on Ko-Fi.
Do not write anything about license or your trial ID publicly there.
You can find your trial ID at the bottom of the purchase page in Symfonium.
This cost a little more than the Play Store price, but since demand is higher than anticipated this is way too much time consuming for me as everything is very manual 
Once the license is activated Symfonium will display Infinite trial at the top of the setting page.
The license is tied to the device so you’ll need to contact me again when you change devices (See FAQ)