I have COPD, I have used a device called Airofit, where you do breathing exercises that you follow on your phone via Bluetooth. I have used it basically for 4 years now on a daily basis, except when sick or on holidays. It strengthens your auxiliary breathing muscles so you’ll find breathing easier. This device is used by athletes, but many people with lung problems have found it helpful. Indeed I have. You will be able to improve your lung volume, hold your breath on both inhale and exhale, thus making you more carbon dioxide tolerant which has many advantages.
i also use an OPEP device, which you exhale into, it forces you to cough, and with the vibrating metal ball inside the device it helps loosen up flegm in the lungs so you cough it up.
I also have an oxy/pulse meter, I have good levels 98-99%. But one would expect this seriously deteriorating whilst having a lung infection. So test again when you don’t have an acute infection. I use several other tools, won’t go into here unless you’re curious/interested.
There are useful supplements, NAC (helps thin mucus), Mullein leaf, Boswellia (LOX-5 inhibitor), all of these help lessen the production of mucus in your lungs. When inflammation is in your airways, your body tries to over compensate with the production of mucus, so those supplements work on dampening the constant inflammation.
Best of luck, take care.