Yes. A few community-suggested options are:

• FroKnowsPhoto: they’ve offered weekly RAW files for editing practice, with forum feedback and Lightroom edit walkthroughs.
• Free retouching/practice RAW collections: some sites provide RAW files specifically for practice and portfolio-building.

Also, creating your own RAW files can be one of the best ways to learn. If you have a camera that shoots RAW, try:

• shooting the same scene at different exposure compensation settings (for example, under- and overexposed frames) to practice recovery,
• using program mode with auto ISO and auto white balance to produce mostly correct files that still benefit from adjustment,
• photographing a variety of subjects to see how different scenes respond to editing.

For HDR-related practice, shooting your own bracketed exposures is especially useful because you can control the scene and exposure range.

So the short answer is: yes, free RAW files are available online, but making your own test shots is often just as valuable for learning Lightroom basics.