I did a clear install of LineageOS 16 on an HTC m8 and Syncthing 1.2.2. Everythings run fine. Yesterday, Google Play Store updates Syncthing to 1.30. After few minutes later my phone reboots by itself. After it came up again and maybe 30 seconds later, the phone did reboot again. This happend until I managed to disable Syncthing. Also the phone got hot.
I have another HTC m8 to install and did also a clear install of LineageOs 16. I also installed Syncthing 1.30 from Play Store. A few seconds after starting Syncthing and granted all necessary rights, Syncthing began to create its key and the phone rebooted by itself.
Maybe with release of version 1.30, there seems to be somethong wrong. Two working and clean installed phones get in boot loop after Syncthing 1.3 was installed. Version 1.2.2 works fine on it.