Is there a way I can link a Homebrew I made so as to get feedback, say, over Discord, without having to publicly publish the Homebrew?

You can drag highlight the homebrew, copy it, and then paste it into a forum like this:

Firebrand Longsword

Weapon (longsword), very rare (requires attunement)

 

You have a +1 bonus to attack and damage rolls made with this magic weapon.

You can use a bonus action to speak this magic sword's command word, causing flames to erupt from the blade. These flames shed bright light in a 40-foot radius and dim light for an additional 40 feet. While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits. The flames last until you use a bonus action to speak the command word again or until you drop or sheathe the sword.

This Longsword has 3 charges. While holding it, you can use an action to expend 1 or more of its charges to cast the Fireball spell (save DC 15) from it. For 1 charge, you cast the 3rd-level version of the spell. You can increase the spell slot level by one for each additional charge you expend.

The sword regains 1d3 expended charges daily at dawn.

Proficiency with a longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

IamSposta

"Into a forum" meaning I'd first post it, say, as a post in these here forums and then link that?

Maybe I misunderstood you before. What are you linking and where are you linking it?

Linking a homebrew, like the one you posted up above, into Discord

Perhaps one way to think of it would be "how would I show my homebrew to someone who has no D&D Beyond account at all?"

If posting in this forum and linking the forum post is how, alright.

If there's a better way, I am interested.