BIP39 and HD wallets are really fun to play with.
Here is a few pages with great, useful tools.
https://iancoleman.io/ (especially the very first link there).
SSSS , SLIP39, Multisig, Entropy tools - also so much handy.
Another HTML page, also based on Java script, is this:
https://3rditeration.github.io/mnemonic-recovery/src/index.html
which allows quick and easy finding ANY missing word (not necessary only last word can perform as check sum , Any word can)
Warning:
better be online while playing such games. And be extremely careful with data behind the real crypto funds.
100% OFFline, Live Linux on bootable USB flash - strongly recommended.
There is no such thing as "too paranoid"
soo true
especially now as they can extract data even from completely airgapped systems, THAT DO NOT EVEN HAVE AN ANTENNA (ram just becomes one)
https://peakd.com/hive-122315/@woelfchen/united-states-frequency-allocations-the-radio-spectrum-or-vs-free-communication