Let's figure out where xsane is coming from:

I thought I would look at this, see what happens:

I have disabled the git-sane ppa in 'Software and Updates', which then updated the cache.

Why does it say "but 1.0.27+git20180809-xenial0 is to be installed"??

Pedroski, we need to go back to basics. Those basics are to confirm that your software sources are the standard ones and that all your sane packages are purged. Then we can install from the standard repos. I would like to confirm that we can get to this stage first of all before going any further.

So, let's do that. And, sorry for asking, but please don't divert from these steps for the moment by trying to install packages etc.

If you agree, first let's check the software sources:

Well thanks a lot for all the tips. I think I can finally stop bothering you. I had an idea:

So I thought I would try this:

Which says "libsane-common is already the newest version (1.0.27+git20180809-xenial0)."
But 18.04 is called Bionic, so I thought, 'Purge some more.' I did this:

The above is pretty much what jsbjsb001 suggested in post #2, so he was definitely on the right track and thanks for that, just didn't work with dkpg -r

After that, the following worked. Also, xsane started and recognized my scanner immediately!! That surprised me!

So, now I have to reinstall iscan, but that's not too hard.

Thanks again, sorry to be a bother!

Yay! Congrats. This sort of problem occurs when different repos have clashing versions of packages. For example, repo A might have package A that depends on a package B and another repo has a newer version of package A that depends on an older version of package B, that sort of thing. Usually my advice in this case is to remove one of the repos, remove all the affected packages, and then reinstall them from afresh from the remaining repo.

Yeah, and the upgrade instead of a fresh install did not help.

I try to keep this older laptop and the newer one more or less in sync, because I rely on my laptop for work. If one won't do it, the other can stand in. I bought an ssd drive which was a bit dodgy, although Toshiba said it passed their test when I returned it. Whatever, my marking program went haywire. I had to rely on my older laptop until I got a new ssd.

Add to that, 18.04 is very unstable still, more like a beta.

Next time I will definitely do a fresh install!

Thanks for your tips and advice, much appreciated!

Generally I do an in-situ upgrade for the minor point releases of my Mint distro, e.g. 18.2->18.3, but I do a fresh install for the major releases, e.g. 18.x->19. It takes a few hours to do the fresh install as my system has quite a lot of non-repo software installed and configuration to be carried out, but it also allows me to do a two-yearly spring clean and make sure that my installation and configuration notes are up-to-date

However, what I do is set up new root and home partitions on my disk and use those to install the new version. I then work on getting the new version into shape for my needs, knowing that I can dual boot into the old version any time I want if the new version isn't quite getting something right. Once the new version is working well then I ditch the old version.

This time round I installed the Mint 19 Beta right at the start. There were quite a few things to sort out but I had moved over completely within about 3-4 weeks.

What in particular are you personally finding unstable about 18.04?