I have spent a significant amount of time trying to do this, and it never quite worked out with login.gov because of its unique requirements. If you get it to work, it will not be by a direct approach, unless something else changes.
Here's the main impediment to the direct approach. For login.gov, they use protocol-optional features that implement government requirements for the authentication process to share and verify these NIST IAL and AAL security level information, or MFA auth, or both. At any rate, login.gov requires more than the bare minimum. Nominally, login.gov and power pages both support SAML and OpenID connect, but each protocol has its own feature that can support these additional goals of login.gov and the government. Obviously a forum post is not going to represent the federal law and security standards you would need to know, and that is not the goal of this post, but I am just saying, there are various legal reasons that login.gov uses the protocol-optional features. As technologies, OIDC and SAML do not "require" that these are used, or even that a protocol implementation supports them, but the protocols are complex enough to support such IDPs and service providers who negotiate their own additional requirements. In the case of login.gov, whether you try to use OIDC or SAML, each one requires a service provider to use a different feature that power pages will not support.
Login.gov documentation has a guide for each protocol that spells out the exact requirements, and when you look at those alongside microsoft power pages corresponding SAML or OIDC IDP setup FAQs, each will describe an unsupported protocol feature required by login.gov. At least, that's how it was the last time I checked.
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NOW, that being said, there is more than one way to get anything done, and where there's a will, there's a way. It is likely that there are other identity providers you might be able to try and use, and in some cases, there is a possibility for them to act on your site's behalf, in terms of assuring that the security standards are being met, where another IDP that can check on the IAL/AAL information within its implementation, and daisy-chain the login.gov authentication information to your power pages site. Maybe you could get it done with MS Entra, like with a B2C configuration, or something else entirely that your agency operates. Or rather, since you are probably already at capacity doing your own job, hopefully there is somone else in your agency that works with such things and can help you.
To reiterate, there may be a way that end users of your site will only need a login.gov account, while you might be integrating to a different carefully configured IDP. That assumes a heck of a lot, but I have seen it happen, so maybe it's worth asking around in your situation.
Sorry about the non-answer answer ("It's not going to work" / "Here's a very long story about something that might exist and might work"). I find there are a lot of those on these types of forums.
