A couple without a son (in any form) is never freed from the Pitṛ Ṛṇa and becomes a preta?

Question

In this QnA discussion, we have a remedy for couples who lack a son to clear off their "ancestor debt - "

Manu Smriti:

9.127. He who has no son may make his daughter in the following manner an appointed daughter (putrika, saying to her husband), ’The (male) child, born of her, shall perform my funeral rites.

However, even so then, several couples still will lack any male progeny either in the form of their son or a son from their "appointed daughter", or any "other kind of son". In fact, I personally know of several of these kinds of specific couples (living and R.I.P), who are without any male progeny in any line of succession (from son or daughter), and neither did they "appoint" anyone as such for "after-life rituals".

Question -
So from scriptural perspective, what will happen to those couples (without any male in succession)?
Will they remain as pretas forever? Are these specific couples never freed from the Pitṛ Ṛṇa ? What are the scriptural "remedies" for such specific "sonless" cases?

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Edit:

Although this QnA - Aputrasya gatir naasti svargo, naivaca..naivaca, does answer some of my questions to a good extent, however, as already discussed above:

The remedies offered in the answer like-
(A): Daughter or Daughter's son doing the rituals.
(B1): Doing a Jeevita Shraddha. This is highly ruled out, since this is extremely frowned upon, at least in my community.
(B2): Adoption is not an option too, atleast for the "specific couples", I talk about.
(B3): We don't have a "king" these days, as a last resort.

So the above list of "options" is ruled out for the specific couples, I want to discuss.

Further, "donating a bull" to avoid the preta yoni is a good remedy, however, what else besides it?

Thus, this question is not a duplicate.

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So what happens, if the "sonless couples" doesn't follow even those "remedial guidelines" of Garuda Purāṇa, will they always be unclear of their Pitṛ Ṛṇa and roam as pretas ?

Answer 1

There are other factors that can affect moksha

a)Bhishma Pitamaha’s moksha:Discussed in this answer

Pitr rna did not hinder Bhishma’s moksha.

b)Jaratkaru:

Refer this for the full incident

In the conversation with his ancestors,his ancestors themselves do not mention that Jaratkaru will not attain moksha,or become a pret .

They say that fathering a son will be of higher merit than his austerity.

So the incentive for Jaratkaru is not the possibility of being born in a lower yoni,but rather the salvation of his ancestors,and higher merit.

3)The Promise of Sri Krishna:

Bhagavad Gita,9.25

Sri Krishna’s promise does not have a condition that the devotee should not have Pitr shap,so there is some other factor,again.