Update: 2022-08-12
I have uploaded a twisted 180 degree (straight) connector that changes the orientation of the downspout 90 degrees. I have not tested this for size or fit.

This is a set of connectors/adapters for my home, that are designed to fit my 2x3 vinyl downspouts.
These are similar to a previous design, but are slightly better fitting and include the same scalloped sides that the original vinyl downspouts have. My original design, that can be found in the link, were just plain.
https://www.thingiverse.com/thing:3914254

The current set of these connectors are a 45 degree horizontal design as well as a 45 degree vertical design. Just for fun I also designed a 45 degree twisted adapter that includes both vertical and horizontal angles. There is also a straight joiner.

Since these are tighter fits than the original design I have also included a small test fit piece that you can use to check the print size and make the necessary scaling adjustments.

My printer has a very small print area so 45 degrees is the largest I can print on it. I have printed the 45's on my MPMD without any supports and they fit my downspouts well. I have not tried printing the twisted version yet.

If you would like different angles let me know and I can add them later.

Update: I added a 3" Round to 2x3 Rectangular adapter. All my 3" galvanized is in pretty poor shape so I just made it with a 3" inside Dia. It will fit loose on any of the galvanized downspouts that have the scalloped or angled ends for fitting inside another 3" pipe. It will probably need a hole drilled and a screw inserted to hold against the metal.

I didn't like how loose the 3" galvanized pipe was so I designed a sleeve that can be inserted to take up the slack.