It's another matter that the Church will have to settle, but as far as opinions...

I agree that a phone confession is possibly valid, but that there is still doubt involved.

Agreed that there's doubt.  If any significant number of theologians hold that it's doubtful, then we must consider it doubtful.  I lean toward them being valid because I haven't yet found a clear-cut principle to definitively rule it out.

So, one practical application of this is that in danger of death, where someone has no other recourse, one might attempt to call a priest and ask him to conditionally absolve over the phone.  One may have recourse to doubtful Sacraments in danger of death.

Obviously this should not become some kind of ordinary way to confess and receive absolution, but it may be of use in extreme cases.  I'm also thinking along the lines of a possible new lockdown some day where the churches are shut down even harder than they were last time with COVID.

Agreed that there's doubt.  If any significant number of theologians hold that it's doubtful, then we must consider it doubtful.  I lean toward them being valid because I haven't yet found a clear-cut principle to definitively rule it out.

So, one practical application of this is that in danger of death, where someone has no other recourse, one might attempt to call a priest and ask him to conditionally absolve over the phone.  One may have recourse to doubtful Sacraments in danger of death.

Obviously this should not become some kind of ordinary way to confess and receive absolution, but it may be of use in extreme cases.  I'm also thinking along the lines of a possible new lockdown some day where the churches are shut down even harder than they were last time with COVID.

Agreed.  If someone is dying, and the only way to administer absolution is over the phone, better that, than nothing at all.  The worst thing that can happen, is that it would be invalid.  Epikeia would certainly kick in here.

The priest could also spend time on instructing/helping the penitent make an act of perfect contrition.

Yeah, both could be done, instruction on perfect contrition and a conditional absolution if there's a danger of death scenario.

In the practical order, it must be considered doubtful, until the Church rules on it, since most theologians hold it to be doubtful.  But I've personally (private opinion) come to the conclusion that it would be valid.  I can see no reason why it would not be ... given all the cases (casuistry) where it would be valid that one by one rule out the different alleged requirements set forth.

Sorry Lad that I didn’t respond sooner, I was away. Below is a case from the Casuist, I believe it answers your question. Especially see what I highlighted in red.

What is the Casuist QVD? Does it hold theological weight? Because it does seem to answer the question.

Did you see my post above from the Casuist?

I just saw it now.  I'm still not convinced.  Much of the talk is around liceity.  Where it gets into the meat of it at the end, is in denying that there's a moral presence over the telephone.  I would dispute that.  When you're holding a conversation with someone over the telephone, it would seem to me that there's clearly a moral presence, an exchange of thoughts, interaction, etc.  There are a lot of conflated thoughts that individually do not stand up, such as the penitent needing to present himself to the priest.  What if he's dying and unconscious?  If a voice is required to establish moral presence, then what of people who are mute?  If physical proximity is required, then what of scenarios where a priest might give absolution to a very large crowed.  This article admits that both Divine Revelation and the Church have been silent on the matter, and is deferring to the theologians, and I find myself disagreeing with those theologians.  Even the writer admits that there's a "slight possibility" that there's moral presence via telephone.  That leaves a lot of room for questioning.  If there's a probability, even slight, then why?  If there's no probability, then that should be stated.  There needs to be a solid definition of moral presence.  To me, if two minds are exchanging thoughts over a telephone, that would constitute a moral presence.  Distance per se is no impediment to a juridical act of the Church.  At some point, the Church (i.e. the actual Catholic Church) would have to weigh in on the matter, other than declaring it illicit.  In fact, to me, the Church declaring it illicit almost implies that it would be valid.  We'll have to see when the Church is restored.  But in the meantime, given the possibility (even if slight), in danger of death, it would be permitted.  If I were the Holy Office, I would hold it to be valid but illicit (and possibly invalid by Church law) except in danger of death.

To me, the answer about whether this Father Paul acted prudently should be in the affirmative.  Father Paul gave the absolution conditionally.  If, as is admitted, there's some possibility that it would be valid, it's permitted in danger of death when there's no other alternative, as was clearly the case in the Father Paul scenario.  Question was not whether it was valid, but whether Father Paul acted prudently.  I think Father Paul did act prudently ... whether or not the absolution was ultimately valid or not (he did do it conditionally to safeguard the Sacrament).  To my mind, they were answering the wrong question.

Seconded. It does make sense in a weird way. If one must avail themselves of an alternative, then yes, better this than nothing at all.

Yes, under normal circuмstances, one may not approach doubtful Sacraments, but it is permitted in danger of death when there's no alternative.