For me it depends in whether the publisher has a .deb file available or not. If there's a downloadable deb file, I just install that through apt/dpkg.

I try not to use custom repos anymore because they rarely keep up with the named releases and can introduce library conflicts.

If I can only get a tarball of the precompiled binary then I'll unpack it in /opt and drop a soft link to the main binary in /usr/local/bin. This is how I handle Firefox and Thunderbird at least.

Otherwise, there's containers (Unif controller, for example) and flatpacks as a last resort.

I personally hate building and installing from source, but I'll do that if I absolutely have to.