It depends on the type of case and the court/tribunal
The idea of a skeleton argument is that it saves time for the court or tribunal, and helps the barristers present their case effectively and efficiently, if they supply to the court/tribunal and to each other, a week (say) before the hearing a bare written "skeleton" of the arguments they intend to advance. They then put flesh on the bones, to continue the metaphor, when making oral arguments.
In a trial - when evidence is being produced and tested - the barristers' skeleton arguments may be very skeletal because the arguments advanced at the end of the trial depend on the evidence so it is only very high level points which would be in a skeleton.
When it comes to appeals, however, skeletons are typically longer because all the facts and evidence is known and so the arguments to be advanced can be more precisely formulated.
Many courts in England and Wales require skeleton arguments to be filed at the same time as the Notice of Appeal so, in that case, they may be filed many months before the hearing and sometimes a supplementary skeleton argument is provided by one or both barristers a week or so before the hearing.
The skeleton argument filed with the Notice of Appeal is part of the court file and should be available to anyone who asks for a copy (and pays the standard fee) at the court office. Some courts require barristers to bring to the hearing additional copies of main and any supplementary skeleton arguments to be given to court reporters and accredited journalists. For example the practice direction for the Court of Appeal states
Documents to be provided to court reporters at the hearing of an
appeal
33(1) Where a party is legally represented at the hearing of an appeal,
the legal representative must bring to the hearing two additional
copies of the party’s skeleton argument (including any supplementary
skeleton argument) for provision to accredited law reporters and
accredited media reporters in accordance with the following provisions
of this paragraph.
(2) In appeals in family proceedings involving a child, the copies of
the skeleton argument must be in anonymised form and must omit any
detail that might, if reported, lead to the identification of the
child.
(3) The additional copies must be supplied before the commencement of
the hearing to the usher or other court official present in court.
(4) The usher or other court official to whom the copies are supplied
must provide one copy to an accredited law reporter (upon production
of their Royal Courts of Justice security pass) and one copy to an
accredited media reporter (upon production of their press pass), if so
requested by them. Those copies are to be provided only for the
purpose of reporting the court proceedings and on the basis that the
recipients may remove them from the court and make further copies of
them for distribution to other accredited reporters in court, again
only for the purpose of reporting the court proceedings.
(5) Any party may apply orally to the court at the commencement of the
hearing for a direction lifting or varying the obligations imposed by
sub-paragraphs (3) and (4). Where a party intends to make such an
application or is notified by another party of the intention to make
one, the operation of those sub-paragraphs is suspended pending the
ruling of the court.
(6) In deciding whether to make a direction under sub-paragraph (5),
the court must take into account all the circumstances of the case and
have regard in particular to—
(a) the interests of justice;
(b) the public interest;
(c) the protection of the interests of any child, vulnerable adult or
protected party;
(d) the protection of the identity of any person intended to be
protected by an order or direction relating to anonymity; and
(e) the nature of any private or confidential information (including
information relating to personal financial matters) in the document.
A direction may permit a skeleton argument to be supplied in redacted
or anonymised form.
(7) For the purposes of this paragraph, “the hearing of an appeal”
includes a hearing listed as an application for permission to appeal
with the appeal to follow immediately if permission is granted.
If you buy a copy of a report of a case - for example from the ICLR - it contains not only the court/tribunal judgment itself (which is also available free from the court website) but also the arguments advanced by each side. These arguments are summarised from the skeleton arguments and oral arguments so this is an indirect way of finding out at least the gist of the skeleton arguments in the case.