I'd like to upcycle an old door for outside?

Check with your local salvage yard to find the one that's right for you.

Some ideas here:

https://www.pinterest.com/tickledpinktony/doors-outside-upcycle-reuse-recycle-repurpose-diy/

Hello. I would consider making a bench or a planter box or something that would be useful to your needs. Here’s a link with some recycling ideas to see if any interest your needs.

https://makespace.com/blog/posts/backyard-storage-ideas-tips-hacks/

20 Simple and Creative Ideas Of How To Reuse Old Doors

https://www.architectureartdesigns.com/20-simple-and-creative-ideas-of-how-to-reuse-old-doors/

here is some info with cute ideas

https://homebnc.com/best-repurposed-old-door-ideas/

I have seen them painted and then adding small brackets to hang pots on for flowers or herbs;

This is so sweet!! https://www.hometalk.com/diy/outdoor/kitchen/upcycled-beverage-station-3919038

Turn it into a great picnic table by adding legs. If it isn't flat add a sheet of plexiglass that also preserve the surface.

I would put it in a garden and attach a window box to it and fill it with blooming plants.

Paint with exterior paint and stand up. Add plant holders to it for a unique garden.

Hi Les: One thing you could do is to make a trellis and a door frame and put it on one side of your patio. Attach the door to the frame and leave it open to the yard to welcome folks to enjoy the grass and whatever else is in the yard.

Good luck

You could make it into a work bench/storage space: https://www.youtube.com/watch?v=mAj9AZ8m644

Use it as a trellis for plants