How to generate legacy receiving address in Bitcoin core 0.19.x.x
From within the GUI, no, and this is intentional. There is no reason to use P2PKH addresses anymore. If you need backwards compatibility, then that's what the P2SH checkbox is for.

But if you really must have P2PKH addresses, you can configure Bitcoin Core to only use them by adding addresstype=legacy to your bitcoin.conf file. If you want your change to also be P2PKH, you will need to set changetype=legacy as well.