I have previously successfully been using the USB serial gadget as terminal on the Nanopi R2S.   The last working release I have tried was: Linux 5.4.45-rockchip64 #20.05.3 SMP PREEMPT Wed Jun 10 11:47:27 CEST 2020 aarch64 aarch64 aarch64 GNU/Linux   Now I am running the following version (Also tried 20.08.08) and the gadget mode does not work after boot. Linux 5.8.14-rockchip64 #20.08.10 SMP PREEMPT Tue Oct 13 16:58:01 CEST 2020 aarch64 aarch64 aarch64 GNU/Linux