Optional rules for a DM to compensate for lack of healing in party?


Context

The party in my game consists of two ‘ranged damage dealers’ and two ‘tanky damage dealers’ (resp. revised ranger and warlock + paladin and fighter), but it doesn’t have a healer. I don’t want the paladin and ranger to feel ‘forced’ to pick healing spells, especially since that’s not the type of character they want to play. The party is currently level 6, and until now they weren’t on the brink of dying too often… However, as enemies are getting smarter, the damage dealers in the back will get focused on more frequently, for being the biggest threat. And I notice I’m holding back as DM quite a lot in this regard. I’m also looking for ways that players can recover from big sudden AOE explosions, during battle, which occurs more often at this tier of play.

Examples

On YouTube I see some DMs let a party pick a support NPC to tag along. This can offer interesting options for plot development, but this also feels a bit too ‘heal-botty’. So this isn’t a solution that is satisfying for my case because it takes away quite some of the strategic decision making at the table. And we all prefer challenging encounters.

In their loot I’m including more potions than I would have otherwise, as well as Spell Scrolls with healing spells. The reason why the potions are not completely satisfactory to me as a DM, is that:

  1. I have the hunch that the party suffers from a dependency on Healing Potions in how this effects their ‘action economy’, and
  2. I’m curious to alternatives for more versatility in combat.

What do the books offer for how player characters can regain Hit Points during battle, without using class features or spells?

Do the books offer other options, without relying on dedicated support characters? I do realise that support goes beyond healing, but options for healing is the focus of this question.