No need for the publication to share homebrew. Creating a campaign and let the player join is still the best solution to share. (no need for a Master Tier subscription).

If they are in a campaign with you, it is shared even if it is private.  To use it in the character sheet the setting for homebrew content needs to be enabled which can be found on the first page of character creation.

Hover or click on My Content and select Campaigns.

If you do not have a campaign set up on D&D Beyond click on Create a Campaign. Otherwise, click the View Campaign link in the box for your campaign.

View your campaign and at the top to the right is a box with a link. This is your "campaign invitation link" (we'll call it an invite link). You need to give this invite link to players who will be in your campaign. When they use it they will be given an option to "create" a character, add a character they have previously created they are not using in a different campaign or use an unassigned one (this is one that has been created previously but not assigned to any player). They can use either link to get a character in your campaign. They can Edit the character and on the Home screen of the Edit Character pages they can ensure that Homebrew content is on (switch will be blue). If it is, they can use any homebrew content in your private homebrew collection (i.e. homebrew made by you not yet published).

The Master Tier Subscription is only needed to share public homebrew and purchased content.