One of the best targets is the genome replication enzymes because they do something that is very uncommon in humans - convert RNA into DNA
The SARS-CoV-2 genome is not converted to DNA during viral replication. It's RNA to RNA.
... this means the viral enzyme that does that can be blocked without harming the host. Nucletotide analogs are king amongst these.
These drugs are analogues of nucleosides that are also extensively used by our cells, so they clearly don't just inhibit anything that happens to bind nucleosides. It's not immediately obvious why some of them inhibit viral enzymes and not enzymes our cells use.
This recent article reviews a few different nucleoside inhibitors with respect to SARS-CoV-2, although doesn't mention the ones in the article above. It's technical.