I thuink it depends when the cover is, and for how long.
I had to go home unwell in the middle of the day - on one of the last days of term. As my class TA was already with the class, I was able to brief her fully on the necessary lessons before I left the building. As we were in the last few days of term, these were consolidation lessons, not lessons with significant new learning.
The following morning, she handed back over to me with a thorough debrief, and so I could pick straight back up again.
This worked much better than the school having to bring in a supply teacher ON THIS OCCASION, especially because the supply teacher would not have been on site for me to brief before leaving.
However, at an earlier point of term, with lessons containing significant new learning, and for a longer period, I would want a supply teacher to cover - for this class.
On the other hand, for my class last year, with an extremely complex mix of severe SEN and behaviour problems, I would NEVER have wanted an unknown adult to take the class. Partly for their own safety, but also because the very careful structures put round each of the children with particular needs for every single part of the day - avoiding all the key triggers, being aware of the safeguarding issues, the key vulnerabilities, the difficult moments of transition etc etc - and the fragile bonds of trust with any adults at all, were so easily broken and so hard to rebuild. If I had been ill last year, then unless SLT or a school HLTA stepped in (our HLTAs have teacher training), a number of individual children would have had to be moved elsewhere within the school with assigned adults (taken from other classes if necessary) before a 'general' supply teacher could have been used.