I would recommend getting a Code Signing Certificate. This allows you to sign your executable, which should help prevent tampering, should reduce false positives (Signed binaries are treated a little bit differently by heuristic/general scans, for most antivirus/etc software), and should boost user confidence in the software.

I question the benefit of actually packing with UPX though. If we were talking about metered bandwidth for downloads, a zip file or a standard installer has the same reduction benefits. And I don't know about anyone else but it's not going to make one iota of a difference to me whether a random executable is 5mb or 10mb. I can't fit anything extra on my hard drive because the executable was packed down to 5, etc. Besides: it's your whole program, 5mb vs 10mb is negligible in 2019. In my book, the main reason to use a packer is to try to hide things from analysis, which subsequently is why those antivirus products treat it poorly.

So my second recommendation is to just drop UPX packing.