I use my gimp 2.8 a lot and can't afford to blow it up until I'm sure that 2.10 works for me.

If I install 2.10 will it just upgrade my 2.8 install (which I do NOT want)?

Is there a way to install so it leaves 2.8 alone?

short answer is No.

Is this for Windows? - Your should always state your OS for this type of question.

For Windows.

The easy way. Install Gimp 2.10 Install a portable version of Gimp 2.8 Run both side-by-side

A more difficult way. Gimp 2.10 shares the same directory structure as Gimp 2.8 usually "C:\Program Files\GIMP 2" so uninstalls Gimp 2.8 first.

What it does not remove is your Gimp 2.8 user profile, any brushes/scripts/plugins there are copied to the new Gimp 2.10 user profile. "C:\Users\your-name\AppData\Roaming\GIMP\2.10\"

The procedure would be

Install Gimp 2.10

Rename "C:\Program Files\GIMP 2" to maybe "C:\Program Files\GIMP 2-bak"

Install Gimp 2.8

Rename the new "C:\Program Files\GIMP 2" to say "C:\Program Files\GIMP-2"

Rename "C:\Program Files\GIMP 2-bak" to original "C:\Program Files\GIMP 2"

Fix-up shortcuts for the two versions.

I did a short 5 minute video for someone on the subject. Might help

https://youtu.be/L9oP_MjGYVA

rich: www.gimp-forum.net

Thanks for that! Yes, sorry about not including OS (Debian Stretch). I had to re-do my question about five times because the system kept rejecting it as spam. I finally realized I had my VPN on and that might be the problem. Sure enough :P

So it sounds like if I can keep separate dirs for the two installs, it'll work. I think maybe I'll try copying my current gimp2.8 to a back-up dir first, and see if that saves me the trouble of reinstalling the earlier one. ???

Anyway, I know what to try. Thanks again.

You will not be able to do that in linux. You would have to compile with a different prefix

There are portable options. I use Kubuntu 16.04 which does not look like it will update (easily)

The flatpak works (sort of, with a few tweaks) There is an appimage that works but not able to add plugins and scripts to it so of limited use.

Looking at my installed flatpak 2.10.0 I think there will be a 2.10.2 along very soon. I would hang on to your Gimp 2.8.x for now.