I am using following link to run polkadot relay chain and connect substrate parachain node with it as parachain.
I downloaded the plain chain spece from following link as described in above toturial:
./target/release/polkadot build-spec --chain plain-local-chainspec.json --raw --disable-default-bootnode > raw-local-chainspec.json
Error: 0: Other: Error parsing spec file: invalid type: null, expected struct GenesisConfig at line 84 column 34
I tested against following versions of polkadot: v0.9.29 v0.9.32