We don't get as cold as you. But the Ultra does fine at our low temps of 0 or just under.
If your baseboard is sized to heat your house at water temps under 200°F, the Ultra will work fine for you.
As you probably saw, it comes with OD reset as standard.
It can be programed to do a quicker or slow water temp increase as the application needs.
As far as problems with the aluminum block. Nope. The Ultra comes with a 15 year warranty on the block. Most SS are 10, and 1 or 2 are 12 years.