It is perfectly safe to freeze salsa and is a good alternative to canning with the shortage of canning lids.  When freezing you do not have to be as careful with your recipe because botulism is not an issue with frozen foods since the foods are not stored at room temperature in an anaerobic condition.  This gives you the option to experiment with different ingredients that are not safe to add to salsa if you can it.  

Frozen salsa will be a little more watery than canned salsa since the freezing process breaks down the cells of the food more and the moisture is released.  You could add a can of tomato paste to your salsa recipe to thicken it a little or add it when thawed if it is a little runny.  

Personally I freeze several recipes of salsa every year and then use them in soups.  They that add amazing flavor to vegetable soups such as beef barley and even chicken vegetable noodle soup.  

Good luck finding lids for canning.  I have had some luck finding lids when I shop early in the morning. Several stores stock shelves at night so they are available when the stores open but usually don't last long.  Hopefully there will be more of a supply when canning season actually starts.  

Good luck canning and freezing and thanks for using Ask Extension

Nellie Oehler