Hi !
Since you don't need XLR for this (Line level balanced inputs/outputs will do) You could go for any good interface with enough in/out
i have a few Motu Ultralite AVB interfaces that has 6 balanced line ins and 6 balanced line outs + balanced main and two High Z Guitar inputs + 2 xlr mic preamps.
Balanced TRS to XLR short adapters would work for you but I can not recommend Motu Ultralite AVB for linux since the new model is not compatible with older more linux friendly firmware..
You could hower do the same with any decent stable linux friendly interface.
AVLinux has a great 3rd party maintained PDF with supported interfaces that would work on any linux.
Focusrite Scarlett 18i20 maybe ?
Behringer if you dare..I would