@GasperyJacquesRoberts
My experiences in the pagan polytheist communities (both online and offline) means I consider myself quite well acquainted with what pagan polytheists generally believe.
Perhaps it is possible that a minority of pagan polytheists do not believe in literally all of the deities, but they would be an exceptionally small minority, if so.
The overwhelmingly prevailing view is that all deities exist. You routinely find pagan polytheists and occultists who engage with deities from multiple pantheons (they might focus more on one particular pantheon, but if they feel moved to, they'll engage or honour deities from different ones, too.
I can link you to a few examples of fellow polytheist pagans stating that they believe in all gods.
Do You Believe Magic Is Real? | John Beckett
The first line is: When someone asks “do you believe in God?” my standard answer is “I believe in all the Gods.”
The diversity of religions | Golden Trail
Here is a blog post written by a practitioner of Roman paganism, who states that they believe in all deities, including the Abrahamic God. I quote from the blog post here:
As a polytheist, I accept the existence of multiple divine beings. It doesn’t mean I worship all of them, but I acknowledge their existence or, at the very least, I don’t assume they don’t exist just because I don’t pray or present offerings to them. It’s called inclusive polytheism, which is in the exact opposite of the exclusivist monotheism that’s usually used to characterize religion as a whole. Although not part of my religious practices, I don’t deny the existence of Egyptian, Canaanite, Hindu, Chinese, Japanese, tribal African, or American deities. And yes, that includes the Abrahamic Yahweh.
A question from a Monotheist : r/polytheism
This is a thread from the 'polytheism' sub-reddit, in which a monotheist asks polytheists there if they believe in the Abrahamic God. If you read through, it's pretty much a universal 'yes' (the only quibbler is someone who says they believe he has "the potential" to exist), so even that is not an outright no, but admittedly it's not technically a 'yes' either.
Concerning the “Legitimacy” of Contemporary Paganism | Hellenic Faith
In this blog post (by a Hellenic Pagan), whilst the author does not explicitly state their personal belief in all gods, they do say that if someone denies other people's Gods, it weakens the case for their own. This strongly implies that the author themselves believes in the existence of all deities. The quotation is below:
At the barest, to deny the existence of other people’s Gods weakens the case of your own. If you suddenly decide to call another person’s religious experience fake, especially if from or derived from a set of long-standing religions with the historical agency of living, individual Gods, then what value are your own?
This is a video by Norse Pagan Youtuber 'Ocean Keltoi', who addresses the question "Can you worship Gods from multiple pantheons?" (to which the answer is 'yes' and if you watch the full video, you'll see how he explains the history of this happening in polytheism.
The very fact that this is such a commonly asked question ("can you worship gods from multiple pantheons") is strong enough evidence to show that belief in gods and goddesses outside of one's own favoured pantheon is a prevalent (and I would say the vastly predominant) worldview in pagan polytheism. Ocean Keltoi doesn't mention the Abrahamic God here, because the majority of pagan polytheists have no desire to worship the Abrahamic God, but he does not exclude the Abrahamic God from existence.
you're happy to accept that all other god-claims are valid in name if not in form (eg, you appear to believe that Yahweh exists but don't believe that Yahweh is the only god)
I do believe that Yahweh exists. But believing in deities doesn't equate to believing in every single claim about those deities. Yahweh supposedly being the sole god isn't a property of his existence, it's a statement made about him, and one, as a polytheist, that I don't accept. I think he exists, but as just one of many.
It may be worth pointing out that the quotation regarding this in the Bible is that Yahweh tells the Jews, "You shall have no other Gods before me", which surely is an acknowledgement that other gods exist?
It is also said that the Yahweh initially was honoured by the Canaanites as a one God of many (from the Canaanite pantheon) - I quote from the Wikipedia article here:
Yahweh - Wikipedia
The early Israelites likely engaged in polytheistic practices that were common across ancient Semitic religion,[14] because the Israelite religion was a derivative of the Canaanite religion and included a variety of deities from it, including El, Asherah, and Baal.[15] Yahweh likely became conflated with El in later centuries, taking his place as the head of the pantheon in the Israelite religion. El's consort Asherah became associated with Yahweh, and El-linked epithets, such as ʾĒl Šadday (אֵל שַׁדַּי), came to be applied to him alone.
So that surely further undermines the claim that Yahweh is the only deity?