How to troubleshoot inconsistent printer problems?

I suppose the fact that the printer is not called specifically by a printer server (CUPS) is what could be the main issue.

Now, on the compatibility side of things I don't have good experience with Brother but IIRC I might have seen that there are some models that work just fine with free drivers.

You may try install the printer via the web browser, localhost:631 or via the Printer application in Control Center or Settings depending on your DE, about testing printing I find enough to print blank pages from LibreOffice Writer, some text editors might print headers or time stamps, but Writer won't, so is good when you only want to test connectivity.

Hope that makes sense, regards!

As an addendum, CUPS print server, which is also available in Trisquel's repositories, is responsible for taking a copy of a document that is to be printed and add it to a queue so the printer can adequately see it's entirety.

I see there are a some different ways to communicate with a network printer at http://localhost:631/admin/. At localhost:631, as mentioned, is where I find CUPS (had to give username and password for add printer function). I guess I can assume since I reach the CUPS page that it is installed and starts as a daemon automatically when I boot up. There is a cups driver at 'https://github.com/pdewacht/brlaser' and your printer is on a list there as supported. But there is also a version of 'brlaser' I see in our synaptic repository.

If in your shoes I think I would make sure each laptop has CUPS installed and brlaser on top of that for starters.

If you are way ahead of me, please don't be offended, from your post I don't know.

I am using an Epson ET-2800 and I see that it is installed in CUPS and I can see it in, for me, Preferences > Printers as well.

I was once kind of in your shoes and most of my printers were HP and most of the Workstations were the ones with Darth Vader operating systems. My printers were mostly connected via the router but some may have had their own wifi print server operating. I do not remember these things well, but I read that in the CUPS world, drivers are intended to go away being replaced with Internet Printing Protocol so you have several ways to try to hook up to your printer assuming you router is still allowing it.

I could be jealous that you are using Trisquel laptops at work. I could not talk anyone out of the 'evil empire' stuff. It seems like you'll figure out a solution.

I am familiar with the HL-L2390DW as my parents have it. It works with printer-driver-brlaser but the upstream version is unmaintained (though there is a maintained fork) so there hasn't been a release with that particular printer definition. However, it should work if you just manually add a printer with a slightly different number like HL-L2360D that uses the brlaser driver. I'm not sure about the HL-L2420DW but you can try the same thing and see if it works.

If you want to use the HL-L2390DW scanning, it will be available in a future version of SANE - some people including myself independently reverse engineered the scanning protocol (it's actually really simple). I wrote a standalone scanning program in C for my personal use, and I intended to contribute a backend to SANE but put it off for a while. Anyway it turned out that one of the SANE developers had written a backend for Brother scanners around the same time, and it works pretty well. I did provide some information about the protocol that he wasn't aware of.

Cool effort there Legimet. My Epson ET-2800 is not found by xsane. Hears hoping that gets added too.