marmite
soy sauce
fish sauce
worcestershire sauce
dashi concentrate
miso
olives and capers for that puttanesca vibe
parmesan
tomato sauce

All wonderful!

However, when avoiding salt completely, these options also work for me:
garlic
smoked paprika
ground toasted sesame seeds (or sesame oil)
making dashi from scratch using kombu and katsuobushi (there is salt in katsuobushi but it's minimal - something like 0.4%)
dried cep/porcini or dried shiitake

This list is mostly about umami flavours. Anything with a strong umami taste is going make things taste good.