I have been doing page design for years. Scribus is the currently the only page layout software that runs on Linux. I have used Linux for years so my first page layout software was Scribus. In the last two years I have used both Adobe InDesign and Affinity Publisher for book design projects. Sadly, InDesign and Affinity Publisher only run on Mac or Windows, so when using them I have to leave Linux behind. All three have all the features needed to create a good looking book or magazine. Why should you choose one over the other?
Why Scribus? ( https://www.scribus.net/ )
Scribus has good solid collection of page layout features
A good number of YouTube how-to videos make for a reasonable learning curve.
Scribus runs on Windows and Mac and is the only option that runs on Linux.
Scribus is free to download and use. No initial cost, no rental agreement.
Why Not use Scribus?
As an open source project with a small number of volunteer developers, changes, improvements, and new features happen more slowly than the paid alternatives.
Why Adobe InDesign? ( https://www.adobe.com/products/indesign.html )
InDesign is the current industry standard.
InDesign subscription comes with access to a huge number of fonts
InDesign has a good number of YouTube videos and training opportunities.
InDesign subscription comes with useful online tools to collaborate with customers or coworkers.
InDesign, is mostly installed and runs locally. But the license is checked over the web and will stop working if you stop your subscription.
Why Not use Adobe InDesign?
The biggest reason not to use InDesign is that it is a rental and the cost.
Why Affinity Publisher? ( https://affinity.serif.com/en-us/publisher/ )
Affinity Publisher has almost all the same page layout features as Indesign.
Affinity Publisher has a modern interface and has regular updates and fixes.
A number of YouTube how-to videos and active community forum.
Affinity Publisher license is not a rental – One purchase price and use it as long as you want.
Why Not use Affinity Publisher?
InDesign is the current industry standard used by more professionals than any other page layout program.
Can you use Microsoft Word ( https://www.microsoft.com/en-us/microsoft-365/word ), LibreOffice? ( https://www.libreoffice.org/ ) or Google docs ( https://docs.google.com )?
The number one reason to use a word processor is that you may already know how to use it.
You will have used it for writing your manuscript.
Both Amazon KDP and Ingram Spark have tools to do-it-yourself starting with a word processor document.
Why Not to use Microsoft Word , LibreOffice, or Google docs?
You can do a lot with a good word processor. But there is a reason that professional book designers use page layout tools. While a Word Processor is designed to facilitate getting your words formatted for a printer, page layout programs are geared to creating print ready PDFs for professional printing. Different tools for different jobs. If Microsoft Word is a hand saw - Adobe Indesign is a laser guided miter saw.
Which is the better choice?
Like so many things the answer depends on what you plan to do. If you are doing page layout for you own book or a friends book Scribus has all the tools you will need. If you want to develop skills for a potential job designing books or magazines Adobe Indesign is probably worth the cost and learning curve. Affinity Publisher falls squarely in the middle and gives more features than Scribus , a more modern look and a modest one time cost rather than a monthly rental.
Feature differences that may matter:
Fonts - One of the features of InDesign is that access to a large collection of premium fonts is included in the subscription. But there are hundreds, no thousands, of good free or low cost fonts. Affinity Publisher and Scribus use the fonts on your computer and if you want another font you need to find a free font or purchase a premium font.
Collaboration tools – If you are designing a book or magazine for anyone other than yourself you will need to share the work in progress and get input from the author or others. At any point Affinity Publisher or Scribus can export a PDF of the work in progress. You can then email the PDF to others for review. A very workable process. It does end up with your client having a number of unfinished versions and possible confusion.
Adobe InDesign includes a web collaboration feature where the author or reviewer can see the work in progress in their web browser and make comments that are returned to InDesign. This is convenient and no files need to be exported or exchanged until the project is finished. The designer retains control of the project files until the final files are approved.
Given you take the time to learn the software any of the three will let you get a good looking book ready for sending to the printer.
I still like Scribus a lot. It is a solid choice and has the advantage of running on Linux (and Windows and Mac).
Affinity Publisher has all the page layout features you might need. It is far less pricey than InDesign. The affinity software offerings seem to have a main selling point of being sorta like Adobe, but not rental-ware.
From my point of view the collaboration tools are the ‘killer feature’ of InDesign and are the main reason I restarted my subscription to Adobe InDesign.