I think it depends on what domain of Cleric you wanted to play as to what would be a good substitute.
Land Druid can stand in well for both heal focused domains, and spell-nova domains like tempest, because the Druid spell list is nice and diverse, especially with the extra spells from land. They also get medium armour and shields, but have material restrictions, which is less of an issue in tabletop but is probably going to cause problems in BG3, unless Larian has put in non-metal magical shields and non-metal armours (like chitin breastplate or half-plate).
Valour Bard would work well as a sub for a more martial Cleric, and while you could turn lore bard into a trickery domain sub, I personally think glamour might work better, but not only is that not a PHB subclass, it also doesn't get medium armour or shields.
