If the wallet is generated from the old bitcoin core wallet I think notepad will work but for the new version of the Bitcoin core wallet, it's encrypted based on what I heard.
Did you add a password to your wallet?
If not try to open it with notepad if you can see the content inside the wallet.dat but if it showing encrypted text well I never heard any tools yet to decrypt the text.
There are various open source tools on github but you would need to specify what you need to extract?
If you just look for addresses inside the wallet you can sometimes even use a hex editor.
Pywallet is widely used but doesnt always give you correct results if the wallet is damaged or is new. It sometimes need modification. If you ate a programmer you can always extract code from github and create your own custom reader.
It is even possinle to extract info from Android phones but that would require some forensic tools
Someone use Pywallet here but it seems he was failed to retrieve the addresses and balances take a look at this post below.
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https://bitcointalk.org/index.php?topic=5084053.0