You have many choices. I pursue a reduced sodium diet and here are my tricks.
Fresh lemon or lime juice accent food at the table very nicely. Similarly, I finish many soups with a little acid just before serving. Also vinegars, rice vinegar particularly as it's not so powerful. Also consider herb and flavored vinegars.
Fat. For most people on low sodium diets, they're usually low fat too. But if you can have it, butter, olive oil and other fats carry flavor well. Seasoned oils too.
Combine acid and fat in a vinaigrette. This can be an excellent accent to most any part of the meal, well beyond salad.
Herbs, fresh and dried. Pump up your use of these healthful seasonings. There are many useful commercial blends as well. Mrs. Dash for the Table (a finer grind and a bit more garlic and pepper than the regular Mrs. Dash) is quite good. Also green onion, fresh parsley, cilantro
Black pepper is often overlooked. It packs a lot of flavor punch.,
Hot sauce. In my view, you're not looking for heat here as much as flavor. Frank's Red Hot sauce is a good one for this purpose and widely available. Panola has a mild red sauce I like a lot too but is hard to find. My current choice is Cholula Garlic hot sauce. At the table, and for seasoning when cooking. But also cayenne and other dried chiles are good sources for seasoning.
garlic and various onions. Fresh and dried, these add lots of flavor.
Salsa. This combines acid, heat, herbs, garlic and so on. Watch labels carefully if you're not making your own. Pace for example is very high sodium. And don't overlook fruit salsa.
Proper technique adds lots of flavor as well.
And while these are still salty, they're less salty:
Adobo seasoning. You can pick this up commercially, but it's easy to make lower sodium and can be quite tasty at about 20% salt by volume. So while you're still adding salt, you're adding 80% less salt. Consider other season salts as options but read labels and serving sizes carefully to understand how much sodium you're really adding.
Pick a good soy sauce. Kikkoman has a decent low sodium soy sauce that's widely available. Still fairly high, but it opens up some possibilities. Somewhat less commonly seen is a low sodium sauce from Angostura, though the main brand labling changed a few years back. Surprisingly low, about 300mg per tablespoon where soy sauce is often over 1200 or even 1500 mg per tablespoon.
Pearl River Bridge light soy (yellow label) has excellent flavor and 800ish mg/tablespoon and is my preference though much saltier than the low sodium sauces out there. And when I say light soy, I don't mean reduced sodium or calories. China has two types of soy, a light and dark. When people say soy sauce, they generally mean light soy sauce. Kikkoman is a light soy sauce.
MSG Heresy to many, it's about 1/3 the sodium by volume compared to table salt. So a pinch here and there can pump up flavor without much added sodium.