I have posted this several times in the past:
Canonists have told us that sedevacantists are not schismatic if they recognize the papacy, do not intend to reject a true pope and act with good reason.
F.X. Wernz, P. Vidal: “Finally they cannot be numbered among the schismatics, who refuse to obey the Roman Pontiff because they consider his person to be suspect or doubtfully elected on account of rumours in circulation.” (Ius Canonicuм, 7:398, 1943)
Not 100% sure if this below canon is the one being referenced above, but it seems to be........
Canon 1325
§ 2. After the reception of baptism, if anyone, retaining the name Christian, pertinaciously denies or doubts something to be believed from the truth of divine and Catholic faith, [such a one is] a heretic; if he completely turns away from the Christian faith, [such a one is] an apostate;
if finally he refuses to be under the Supreme Pontiff or refuses communion with the members of the Church subject to him, he is a schismatic.From what I can find, the quoted reference from QVD is that of a commentary on Canon Law by Wernz, which was later revised by Vidal in 1943 according to the quote - Link:
https://tinyurl.com/2nk8zhv6 If someone wants to translate for themselves...

Rev Ignatius Szal: “Nor is there any schism if one merely transgress a papal law for the reason that one considers it too difficult, or if one refuses obedience inasmuch as one suspects the person of the pope or the validity of his election, or if one resists him as the civil head of a state.” (Communication of Catholics with Schismatics, 1948)
https://tinyurl.com/yc8bpcr5 is a link to Communication of Catholics with Schismatics, 1948
I'm expanding the quote here below, bolding the above text:
The Communication of Catholics with Schismatics
the name of Christian, nevertheless refuses obedience to the
Supreme Pontiff or refuses to communicate with those members
of the Church who are subject to him. 2 There is here involved
no denial of any article of divine or Catholic faith. Strictly
considered, a schismatic professes belief in the sovereign power
and primacy of the Pope, but out of malice refuses to be subject
to him and to obey him as the Head of the Church and the Vicar
of Christ on earth. Such schism is called pure schism.
To constitute the delict of schism in the strict sense, the
following conditions are required:
1 ) One must withdraw directly (expressly) or indirectly (by
means of one’s actions) from obedience to the Roman
Pontiff, and separate oneself from ecclesiastical com¬
munion with the rest of the faithful, even though one does
not join a separate schismatical sect;
2 ) one’s withdrawal must be made with obstinacy and rebel¬
lion ;
3) the withdrawal must be made in relation to those things
by which the unity of the Church is constituted; and
4) despite this formal disobedience the schismatic must rec¬
ognize the Roman Pontiff as the true pastor of the
Church, and he must profess as an article of faith that
obedience is due the Roman Pontiff. 3
As a consequence there is no schism involved if one separates
from his bishop and the communion of the faithful of his diocese,
but remains subject to the Roman Pontiff and the Universal
Church. However, today such a position would be impossible
to maintain in practice. Nor is there any schism if one merely
transgress a Papal law for the reason that one considers it too
difficult, or if one refuses obedience inasmuch as one suspects
the person of the Pope or the validity of his election, or if one
resists him as the civil head of a state. 4
(4 Reiffenstuel, Jus Canonicuм TJniversum (5 vols. in 3, Maceratae, 1760,
Lib. V, tit. 8, n. 5 (hereafter cited Jus Canonicuм); Schmalzgrueber, Jus)