I've also heard often that frequent stops/starts are not good for the miner HW in the long term.  Mostly due to the temperature changes between operating and rest state, thermal dilatation can eventually damage the chips.  If that's the case, it doesn't really matter if stopping is clean or just power-stop.

Yes, a controlled plug is a good solution.
A relatively old S9 is quite profitable with solar power, though amount generated is not so high.
Just out of curiosity, how do you imagine controlling turining on/off the miner?  Some output of the inverter or measuring voltage or so?

I understand and accept the points about 3rd party firmwares being more closed than Bitmain's own, I have disregarded this.
My comment for more openness was a general comment.
I do understand Bitmain's approach and can accept it (make sure their HW is not used in other ways, foreclose revenue of 3rdparty firmware makers, etc), but in general I don't like limiting usage of a HW I own through software (be that a laptop, mobile phone, game console, etc.)

Oh, I see, I didn't know that.  Partly it is understandable from the point of view of the manufacturer, but on the other hand, they should do a much more flexible firmware.
Generally I would be happy with a higher level of openness/interoperability/transparency in the mining HW business.

I was a bit surprised that the Antiminer S19 does not have performance configuration options (like S9), for frequency/voltage, for lower or higher performance (I'm especially interested in running it at lower power).
Is there some trick for this?
Or are there alternative firmwares supporting S19? (Braiins, HiveOS seems not)
I did some search, in this forum too, but found no answer.
S19_95T, original firmware Dec 11 2020, updated to April 11 2021 (no visible differences).

Please grant access to my user catenocrypt, I'd like to contribute to the Taproot support page.  Thanks!