You can support on Patreon for less than the minimum tier. It is just the cut-off over which the rewards (such as stickers here) are given. Support for just $1! He'll still get it!

Thank you, they could make this clearer.

I didn't know this either. I guess that's why many projects have a fake $1 tier with just "the pleasure of knowing you contributed" or something like that as the "reward" for that tier. To let people know that that's still an option.

I agree, I would have signed up for a $1 tier or perhaps $2 but $15 is far too high for the minimum tier. I support the Zig author for $1/mo and hope others would do the same for my open source projects in the future.

Apart from knowing that 15 USD monthly is not a minimum possible donation there, please see other possibilities to donate on the official link for donations (also posted here). Patreon is only one of the options.

Don't let "it's not enough" stop you. Make a one time payment of what you can afford within reason. They don't expect you to put yourself out.

The minimum donation in Bitcoin is probably about US$0.01. Anyway that's what I've paid in transaction fees the last few times I made a donation where I didn't care how long it would take. (They were confirmed within a few hours.) Transaction fees for within-the-hour confirmation are around US$0.20.

If you go to wireguards donation page, you can make a one-time donation too.