Ok thanks a lot, the RPC command works with this flag.

But wallets are still not read:


$ bitcoin-cli -testnet -datadir=/Volumes/Crucial\ X8/bitcoin/Bitcoin/testnet3 listwallets
[
]


Don't understand why

2024-03-20T14:20:00Z Using wallet directory /Volumes/Crucial X8/bitcoin/Bitcoin/testnet3/testnet3/wallets
2024-03-20T14:20:00Z init message: Verifying wallet(s)…
2024-03-20T14:20:00Z Using /16 prefix for IP bucketing