Delegated Microsoft Entra ID user account

Question

At my company, we'd like to have an M365 user account that we share among certain administrators. This is to enable the use of certain external services that only allow a single user account and that we need to manage together.

Can we do anything better than sharing credentials? I feel there should be a way to do this, but I can't find any. I searched for delegated user accounts (didn't find anything useful), impersonation (but that's something else), and shared accounts. For the latter, I found Microsoft Entra ID account sharing what sounds like something interesting, but I couldn't find any information about it apart from this single page (and this page doesn't help much, apart from pointing to docs from the time of the Azure Management Portal).

Note that while this is about Microsoft Entra ID accounts in the end, I think it's an important context that we work in M365. FYI I also posted this to Reddit but didn't get any replies. I reopened this from Microsoft Community.

Any help would be appreciated.