Are you saying Germanic U106 also came into Europe from Iran in the 1st millennium BC, but speaking a wholly different (Rhaetian) language to other Germanic (IE) migrants from Iran?
If so, how is there an early 2nd millennium BC Swedish U106 sample? Why would phylogeny suggest U106 development around Sweden and the Western Baltic pre-2,000 BC?
And why would Swedish Bronze Age samples be such a close match to modern Germanic U106 samples autosomally?
R1b1a is an European haplogroup and it came from Europe to Iran, not vice versa. We know even in the first centuries of the 1st millennium AD, some different non-Indo-European peoples, such as Etruscans, Iberians, Basques, ... lived in Eurupe and R1b was the main haplogroup of these people. U106 actually became a Germanic haologroup after adopting the Germanic culture in 500 BC.