this is one of those things i wouldn't pirate. maps and weather are extremely important when sailing and having legitimate sources of these things is something you should be doing. you wouldn't pirate a first aid kit would you?
I would buy charts if you need them for life and death reasons but if you are open to using older charts for interest and leisure purposes you could use the CM93 chart set. This is a world wide set taken from possible copyrighted sources and crowdsourced info. Of course we cannot direct link to potentially copyright infringing files from here but this thread on cruiser forum discussing the charts may point you in the right direction.
Not sure if they work on garmin natively but they are fine with opencpn.
Remember they are about 10 years old and come with no guarantees.
Failing that openseamaps is pretty good, though lacks bathymetry data.
Pretty soon we'll be hearing from people asking about finding free planks to walk, peg-legs, treasure maps, trained parrots, eye patches, and rum. Yo-ho-ho!
I tried pirating the training maps for the „Sportbootführerschein See“ (German drivers license for boats in German waters) and had no luck.
I would not bother pirating this for two reasons:
The only valid maps (for German waters) are made by the „Bundesamt für Seeschifffahrt und Hydrographie“ and all maps are a licensed copy. They put a lot of work into maintaining and updating those maps and one way to maintain the infrastructure for safely traveling is paying for it.
Your life could depend on an accurate map. The official maps I found were updated every 10 days. Would you risk it for a couple of €?