I'm not necessarily looking at being able to swap between 1.75 mm and 2.85 mm with the same hot end. I'm looking to use the same form factor for both. The same, or mechanically compatible, external dimensions.
You can fix the video stream by doing a "Cura Connect Reset" this solves the problem by now, but it can come back again. A downgrade to get rid of this problem will not help, because this problem exists also in former firmware versions.
If you want to downgrade you need a recovery image and an SD card. There are some threads here with instructions on how to do it.
Today I offer you Ultimaker Print cores which I bought some time ago for printing projects.
I have two BB0.4 (brand new, never used) and AA0.4 (used once for like 15-20min print) and AA0.8 (used once for like 15-20min print).
So all in all, they are new, and I do not need them anymore.
Price: 90eur each (negotiable)