Hi!
I’ve written down the steps I took to have L2TP/IPSEC from my S8 with Android 9 to my Mikrotik.
http://forum.mikrotik.com/t/creating-l2tp-server/135651/12
The config is done in WebFig but I guess you can translate them to CLI.
Why would you leave the VPN on when at home on Wifi? It takes 2 seconds to disable it.