I've been hosting my application on a 3B+ for years. What makes the Pi different to any other machine that you have on your home network? Assuming you have a static IP, all you have to do is forward ports 80/443 (or whatever) to the right machine/ports.

They're great little machines for this exact purpose. No need to have a full blown PC serving trivial stuff. Only problem is, they use SD cards and eventually. I've had a quality 128GB card in mine that has died/been corrupted about 3 times in 4 years. That's my biggest issue with these amazing little machines