There are a range of free and paid for maps available as GeoPDF and GeoTIFF for download for Australia (information current at Jul 2024)

Geoscience Australia has many maps of various scales (1:50k, 1:100k, 1:250k, 1:1m) available as GeoTIFF for free download

https://www.ga.gov.au/scientific-topics/national-location-information/topographic-maps-data/topographic-maps

The level of free digital mapping available varies widely from state to state. Some areas of the states are reasonably well covered by free Geoscience Australia maps (eg the Kimberley, Cape York). In rough order of how useful and free the GeoTIFF/GeoPDF maps are by state (at 2024):

NSW Spatial Collaboration Portal has a wide range of maps of various scales (1:25k up to 1:100k) in both GeoTIFF and GeoPDF formats, for various years, available for free download:

https://portal.spatial.nsw.gov.au/portal/apps/webappviewer/index.html?id=06e3c2e0de1e4efda863854048c613c6

The QTopo service has free GeoPDF maps of various scales (1:10k up to 1:100k) that can be downloaded.

https://qtopo.information.qld.gov.au/

TASMAP has a range of maps of various scales (1:25k up to 1:250k) in both GeoTIFF and GeoPDF formats available for purchase at a small cost (~$2 each)

https://nre.tas.gov.au/land-tasmania/tasmap

Vicmap has a range of maps of various scales (1:25k up to 1:100k) in GeoPDF formats available for purchase at a cost (~$8.50 each)

https://vicmaptopo.land.vic.gov.au/

Landgate has a range of maps of various scales (1:25k, 1:50k, 1:100k) in locked GeoPDF format available for purchase at a cost (~$15 each). Due to locked format, not sure if these can be converted to GeoTIFF:

https://www.landgate.wa.gov.au/location-data-and-services/maps/topographic-maps/

Currently does not have GeoTIFF/GeoPDF maps available

Covered by NSW

Covered by Geoscience Australia maps

(This page overlaps with the answer to question Seeking Australian Topo Map GeoTIFFs).