I cannot find out (despite trying really hard) how I can add a Czech spell-cḧeck dictionary to UE in Linux (Mint 19.2). Can anyone help me?

I managed to get my English dictionary installed & working by installing aspell and aspell-en from my normal system package manager. As soon as I had aspell & a dictionary installed onto my system, I was able to save my own words, & everything started working as it should.