Yes, you can schedule Google My Business posts (aka “updates”) for free with OneUp (screenshots of how OneUp works below).
Scheduling Update, Event, and Offer posts are all supported, as well as scheduling images to the Photos section of Google My Business.
Google My Business (aka GMB, Google Business Profiles, or GBP) posts are great and can help your SEO.
However, you’ve probably noticed that there is no way to schedule GMB posts for the future inside the Google My Business dashboard:

To schedule Google My Business posts for free, you can use OneUp
And yes, OneUp has a Free Plan 😊
How to schedule Google My Business posts for free
Using OneUp, you can schedule posts to Google My Business.
First, connect your Google My Business location(s) on the Accounts page:

Then click Create A Post.
Then select which GMB locations you would like to post to (if you have more than one connected). You can post to multiple different Google My Business locations at the same time:

Then create your GMB post, and add your image:

You can even click the “Auto-generate caption” button to have your post’s caption automatically written for you.
Then choose whether you would like to also add the image to the Photos section of Google My Business, and choose whether you want the post to be an Update post, an Event post, or an Offer post:

You can also choose “None” if you ONLY want the image to be scheduled to the Photos section of your Google My Business locations – and not publish as a Post.
You can check out the post preview in OneUp to see how your post will look once published on GMB:

OneUp supports all Google My Business CTA button types (Learn More, Call, Book, Sign Up, Order Online, and Buy).
In addition to just scheduling posts, OneUp allows you to set GMB posts to automatically repeat at whatever interval you choose. For example, this post will repeat every week:

Then either post it now, or schedule it for a date in the future, or save your GMB post as a draft.
Replying to Google My Business reviews
In addition to scheduling Google My Business posts, OneUp also supports replying to Google My Business reviews:

You can even click the “Suggest a reply” button and get an AI-suggested reply (which you can edit to your liking before submitting):

very nice tool