Alternatives to popular expensive software

Adobe Illustrator

Alternative: Inkscape (https://inkscape.org/)
Inkscape is a free and open source vector editor using Scalable Vector Graphics (SVG) as the native format. It’s lightweight, so will run on quite low-powered computers, but it’s surprisingly capable for a free tool, with a lot of useful features including layers, object grouping, drawing, shape, calligraphy, pencil and pen tools, path simplification with variable threshold, bitmap tracing and Boolean operations.

Adobe Photoshop

Alternative: GIMP (https://www.gimp.org/)

GIMP is a cross-platform image editor available for GNU/Linux, macOS, Windows and more operating systems. It is free software, you can change its source code and distribute your changes. Whether you are a graphic designer, photographer, illustrator, or scientist, GIMP provides you with sophisticated tools to get your job done. You can further enhance your productivity with GIMP thanks to many customization options and 3rd party plugins.

Adobe LightRoom

Alternative: DarkTable (https://www.darktable.org/)
darktable is an open source photography workflow application and raw developer. A virtual lighttable and darkroom for photographers. It manages your digital negatives in a database, lets you view them through a zoomable lighttable and enables you to develop raw images and enhance them.

ArcGIS

Alternative: QGIS (https://qgis.org)
QGIS is a user friendly Open Source Geographic Information System (GIS) licensed under the GNU General Public License. QGIS is an official project of the Open Source Geospatial Foundation (OSGeo). It runs on Linux, Unix, Mac OSX, Windows and Android and supports numerous vector, raster, and database formats and functionalities.