@psherman
Like I mentionned in an earlier message, I discovered that one of my switch is a netgear GS108Ev2 which is actually a managed one.
I bought this one more than 5 years ago, and never managed it because it need a windows software and I had no windows pc at home at that time (and didn't really need a managed switch before).
This switch seems to be kind of "vlan friendly" because I have VLAN 100 from my ISP (for TV) for a long time going through this one.
The buffalo was connected to an umanaged GS316 that I bought recently, thinking it should act similar to the GS108E.
So, as a conclusion:
No VLAN goes through GS316
Some VLAN may go through GS108E managed but not configured, but I didn't tried further and just configure ti.
Now I have tagged what I need on this one, and the buffalo device accepts to tag what I want to tag.
@NPeca75
With suitable switch talking to the openwrt device, Vlan1 is untagged(access) and Vlan11 & Vlan22 are tagged is not problem.
All works perfectly now.