Disclaiming an inheritance is relatively straightforward - you need to file a declaration with the probate court or a notary, and as far as I know, this has to happen within three months of learning about the death. The good news: you don't need to agree on valuations or investigate everything before you disclaim the inheritance. It's enough to just say you're disclaiming it - done. That makes sense if you really can't tell whether debts outweigh the assets and don't want to take the risk.
With cryptocurrencies it gets trickier, because they don't show up at banks. The heir (or if you disclaim, the authorities) would have to look through your uncle's emails, access credentials, hardware wallets, or paper copies of private keys. If there were accounts at exchanges like Kraken, Binance, or similar, they'd need to be notified via the death certificate. Sometimes you find clues in his documents, on invoices, or through transaction histories. The problem: if you can't find access, the money is essentially gone and can't be moved anymore - but that also means it's not an asset you'd inherit anyway.
My advice: talk to an inheritance lawyer or check with the probate court about how much time you have left and whether it makes sense to do a bit of research first. If you're unsure and the debts could outweigh the assets, disclaiming is the safe option. You hand everything over, but you also have no obligations.