I figured it was something the AdGuardHome developers changed. Strange I haven't discovered this option yet, but it doesn't surprise me that the AGH development team changed something again. Do you mind sharing where you read about this option at ? I would like to read more about it to access if it is needed the "average" users use case.
I just read about it here
https://github.com/AdguardTeam/AdGuardHome/issues/6422 , it turns out it relates to the
kernel version on whether the option is needed or not. The option disables the additional congestion-control features added to quic-go in
v0.39.0. Certain older kernels tend to not agree with the changes in quic-go.
The issue doesn't seem like something that would be caused from being in a double nat. Especially if it worked for you before the last update/fix.