I do have a regular framer that I use if pet portraits and paintings are going to be picked up in person, but if I am posting a commission I usually send it unframed for the client arrange framing themselves. As I am living quite a distance away from my framer now, I usually drop the painting off for him to frame and let the client pick it up.
If the client leaves the framing up to me the framer and I will choose something that we feel complements the painting, some clients have a preference ie dark wood, gold or pine, but more often than not they are happy to let me choose something. Sometimes while at the framers I will (pre-arranged) send the client a photo of the frame and mount sample on the painting so they can approve it. Some customers prefer to entirely arrange their own framing.
However during the Covid-19 pandemic I did find an online service which I tried, and will probably be offering this service as the frames are delivered to me. These have plexiglass and so are generally safer to post without the risk of breaking glass in transit.
Below is a sample of framing that I can provide. I will post a selection on my website when I get a couple more samples.