Have you tried postybirb?

i second this

I third this, Postybirb saves a lot of time. You can even upload to multiple sites at once.

Don't know how to use it.

They have a tutorial that may help you understand it better tho
https://www.postybirb.com/tutorial.html

I can't help. I post pictures one at a time. It doesn't take all that long.

does postbirb work?

Don't know how to use it.

Well, I haven't finished my online gallery project so I can't offer that, but I'd say if you don't want to post them one by one, the best thing would be to create a composite image with all of 'em, with a DL link to a dropbox or google drive link probably so people can view the separate pieces or just all at once in one post here on FA?

Mind you, this is probably the closest you can get to what Inkbunny allows. And luckily Dropbox and Google Drive have free options.

Or if you know someone with a web server, they might be able to build you some custom page or something, if you wanted to go all out...

That's pretty smart.