How to downgrade your Bose QuietComfort 35 II from 4.5.2 to 3.1.8 : r/bose
With Bose, users can downgrade the QC35 firmware after months of complaints – NewsBeezer
My new Bose Qc 35 II. I have tested both this and sony XM4 and gone with Qc35II.So much happy specially with 4.8.1 firmware. I wonder it is competing with 2020 XM4
Bose disproves conspiracy theories regarding reduced noise canceling performance with QC 35 II update - GSMArena.com news