The $432/user/year Microsoft 365 E3 subscription[1] covers Windows Enterprise LTSC, has no minimum order quantity, and can be purchased online directly from Microsoft without a volume licensing agreement (by clicking "Try free for one month" on the linked page).
Source: my own "enterprise" has two users, a single Microsoft 365 E3 subscription, and no volume licensing agreement.
Interesting, that appears to be brand new (as of December, anyway), and they certainly aren't advertising it widely. Could be worthwhile if you don't mind subscribing to your OS and losing access if anything ever happens to the account.
I wonder if what it really means is that LTSC 11 is now enshittified.
Source: my own "enterprise" has two users, a single Microsoft 365 E3 subscription, and no volume licensing agreement.
[1] https://www.microsoft.com/en-us/microsoft-365/enterprise/e3
(the "Full Comparison" PDF linked from this page confirms that LTSC is included in this subscription)