Hanafi
The sources give no view for it here.
وقت الإحرام بالعمرة
هل يجوز الإحرام بالعمرة في السنة كلها؟
Each school’s answer
In our wordsHanafi
Not stated in the sources
Maliki
Not stated in the sources
Shafi'i
Not stated in the sources
Hanbali
Not stated in the sources
The texts
مسألة: الإحرام في العمرة جائز في السنة كلها، خلافا لبعضهم، لأنها عبادة تتعلق بطواف وسعي كالحج لأنه أحد الميقاتين كالمكان.
«الإشراف», al-Qadi Abd al-Wahhab p. 467
From the schools’ own books
Maliki
The sources give no view for it here.
Shafi'i
The sources give no view for it here.
Hanbali
The sources give no view for it here.
What is «in our words» is our standard wording; the books’ texts stay as they are.