So the summary of the problem.

  1. Pixel 6 cannot connect SFT1200 with IPV6 turnned on. After turnning IPV6 it can connect.
  2. Samsung smart plug cannot connect to MIFi v3.211 with IPV6 on. But 3.203 is OK.

@temerosoivan can you try GL.iNet download center
and
GL.iNet download center
Because recently we fixed some problems with IPV6. Hopefully it helps.
But if not, we need to check further according to the info you provided.