Questions[deb](ubuntu)

I tried to install some .deb files in Ubuntu 20.04 from GitHub and other internet sources, but when I open it with Software Install it gives me this problem (Failed to install file: not supported). The only way for me to install them is to go to the downloaded file and do sudo dpkg -i file.deb.

Can anyone help? I don't know what to do and I don't want to use the terminal every time.

Any help would be appreciated, thanks

EDIT: that's NOT a problem with .deb in Ubuntu, it is a problem with Software install. I can install every .deb through the terminal but not with Software install, and Ubuntu suggests to install .deb with Software install. That's not a dependencies problem or anything similar, that's an issue with installing .deb WITH Software install and I would like to know how I can fix Software installer

Of course for most packages the answer is trivial: if it's some tool or library, deb is the only option, while for some proprietary software snap is the only option.

It seems Ubuntu is heavily pushing and promoting Snap packages, citing advantages in packaging, isolation, security, updates, etc. yet all applications that ship with Ubuntu 18.04 are installed as deb packages.

One example is Firefox, which is a package that should be kept up-to-date for security reasons, and that in the past had conflicts with distribution package maintainers about security and branding (Iceweasel). Yet Canonical chose to ship Firefox as a deb package.

For packages that have both a snap and a deb, this raises the question: Which one should you install? And if the answer is snap, should I actively migrate installed deb's?

Sometimes, when downloading software from the Internet, I find that there is a .deb package ready for either my Debian/Ubuntu and also a tarball to be compiled. In the beginning I would simply use the package for its ease of installation, and wouldn't even dare attempting to compile. Even the sound of it scared me a bit. Nowadays, however, when I have the option I sometimes find myself in a dilemma: is there an unpopular advantage to compiling from source compared with the .deb package? I hope to find out here, thank you.

Possible Duplicate:
How can I install software offline?

I want to download and save some deb files, and preferably their dependencies, of certain apps, from the repositories (apt-get, aptitude) to a custom location without installing, so that I can install those apps while the machine is off-line. Also I want to know if it is possible to download deb files for a 64 bit machine on a 32 bit machine.

On a RedHat/CentOS system, I can verify the installed RPMs on my system using rpm -V.

What is the Ubuntu or apt equivalent of this command?