RT 5.9 - why appimage?

I'm interested in updating my RawTherapee but I don't like, I don't trust on that appimage system.
Looks like the virus .exe in the old time Windows, only download and double click it ...

It is frustrating when the app you use isn't updated in native packages, but I've gone ahead run the appimage files through clamtk/clamav when its something I rely on, like AnotherRawTherapee (ART) for example.

Yes, it is!
I'm in Linux Mint with RT 5.8.1. We were waiting a couple of years for new properties to Therapee. Now they are making those, but not in deb package.
ART doesn't help in that case, no deb there.

I don't have experience about Mint, but since it's a derivative of Ubuntu and thus Debian, I looked at Debian's package information. Currently RT 5.9 seems to be available as a Debian package in Bookworm aka current testing that will become stable later this year as a .deb:

bookworm (testing) (graphics): raw image converter and digital photo processor
5.9-1+b1: amd64 arm64 armel armhf i386 mips64el mipsel ppc64el s390x

So I'd guess a .deb release might happen eventually.