You can get free labels from UPS. They're supposed to be for use with UPS shipments, like how free priority boxes from USPS are supposes to be for use with USPS Priority Mail shipments. The UPS label mis-use is not a federal crime though, so do with that info what you want. The UPS labels usually have UPS logo and some text on them. More on reddit.com

I switched from UPS to FedEx as I got a much better contract with them. Had a lot of their shipping labels left that I saved for just in case. Whenever I run out of FedEx shipping labels I put the UPS ones in that says UPS shipping only. I'm just doing my part to save the environment by not causing any more waste. My FedEx guy or my mailman never said "Hey this says UPS, you can't ship with these". if you want, just mask it with black marker. But then there becomes a point, would you rather go through all this for a few cents a package? Long story short, use the labels to deplete what you have and not create waste. If you're doing it to save a few cents, try to find other ways to increase your margin that will make you sleep better. More on reddit.com

First couple of UPS Label batches worked well on my rollo, got over 10,000 orders out using them for free for the past few years. Reordered about 15,000 of them and now i’m going through the same stuff. Printer is clicking and getting stuck right before address. Rollo support said it’s due to the thickness of the UPS labels and some batches are bad. More on reddit.com

PSA: Thermals are no good for stickering! They fade! Thermal labels dont accept ink like normal stickers do. The ink sits on the surface and will fade in rain/sun. If you want your stickers to last more than half a year outside please avoid thermals. More on reddit.com