There is no such thing at this time. GIMP 3.0 will be ready when it’s ready. The developers might announce a release date later, when the software is nearing completion, but the haven’t, and i don’t expect them to do that soon.
Don’t hold your breath, though. I don’t expect to see 3.0 in 2023.
I just discovered that the gimp has 3760 issues open. Maybe bug triaging would be something where I can imagine that the devs could need some help. I.e., reproducing bugs, finding out the root causes, asking the reporters for missing information etc. Maybe a good way to familiarize with the code (while learning C).
Here is annual report and plans for 2023 2022 annual report - GIMP
Maybe it would be the best to freeze 2.10 development and work out roadblocks for 2.99 and 3.0.
3.0 would come faster this way.
Also, I would assume GTK 4.10 will release this year (latest unstable is 4.9). Will porting over to GTK 4 be beneficial for future development?
2.10 is pretty much frozen - only bug fixes and easy backports are really being added now. For example, I knocked out a few backports over the span of a week or so, then went back to working on the GAction port for Gimp 3.0.
2.10 is still what a large number of people use, so it can’t be completely ignored.
I just wanted to say that you are doing a great job for GIMP!
From introducing CMYK mode, porting resynthesizer and other plugins, improving PDF export, PSD imports and tons of other contributions is an incredible achievement that will bring GIMP into a new era.
Thanks, glad I could be helpful! Pretty much everything I’ve done has been built on the work of others - I just added a little more to it. That’s the nice thing about open source software I think.