What is a good (simple) method for resizing photos so they can be posted here?
Thanks for any help.

https://www.adobe.com/express/feature/image/resize

An account is required (simple email and password), but Adobe offers this free online resizing tool. Other free services may plaster their watermark all over, or steal your file for their own use.

I use "Paint", which comes automatically on PC's. The controls are in the "Image" menu box. I crop the photo to remove what is unneeded, then resize what remains to 1,000 pixels maximum, then "save as", making sure that it is saved as a jpeg. Easy.

Thank you fellas. I did have an Adobe photo kit on an older computer.

Irfanview is one I use for quick edits rather than using firing up Photoshop which is great for heavy lifting. https://www.irfanview.com/. It's pretty easy to crop, physically resize and downscale the DPI. You'll get the best results for uploading to the web at 72dpi for JPG images. Keep your file size under 350k for RYPN if I recall correctly.

Faststone Photo Resizer.

Another vote for Irfanview

If you have an Apple computer with Preview, Control click the .jpeg and select Open With, open the .jpeg with Preview, go to the Tools menu in Preview, and select Adjust Size. Or you can open Preview first, go to File, and select Open and you will get a window of files to select from. Click on the .jpeg you want to resize to select it and then hit Open on the lower right of the window to open it and proceed to the Tools menu as before.

The low tech way is to use the resizing feature in Mail. Just email yourself a copy of the .jpeg and resize it to the size (small, medium, or large) that gives you the file size you need.

Thanks again for all the help.

I use Xenforo for the forums I run, and it has options to automatically resize images to a size the webmaster specifies. I would suspect that PhpBB also has the same capability? I vaguely recall it required a bit of changes to the default setup, but it wasn't bad.

Also, should there ever be a need to move the site, I would be interested in adopting it and converting it to a Xenforo type forum like this one:
https://railroadforums.com/forum/index.php

Irfanview is the official exclusive photo processing provider for the Alternative Examples paint color thread, mostly because I didn't have to pay anything for it. :)

Yes, you can have phpBB automatically resize the images to fit with a few code changes though I'm pretty sure that's not activated, just max file size which kind of makes you guess until the image shows up in the preview.

Sounds like it works the same way then. I had to install some sort of image processing program on the server, but it was free and easy to install. Then I told it both when to resize (over 2048 px) and also what was the maximum size it would accept for starters. Don't want somebody uploading a 48 meg file and taxing the server too much.

I also have a feature that supports drag and drop of photos. Having those two made photo posting much easier and it happens far more often now.

Drag n drop is a great feature. Dunno if the latest phpBB version does that either internally or with an extension.

Another vote for Irfanview. I have been using it for graphics and photos now for over 20 years and it not only resizes, it does a 95% job on color restoration as well. I use it for all of my graphics applications for work as well.