Telstra are currently discounting their month to month mobile broadband plans that are $25 and above per month (no discount on the $15 per month plan). Data allocations are pretty low but might be a handy back-up, plus there are no excess data charges. The monthly discounts are removed after 12-months of service.
Small: $25 per month for 10gb - now $15 per month (includes 5g access to 30 June 2020)
Medium: $50 per month for 50gb - now $40 per month (includes 5g access)
Large: $75 per month for 100gb - now $60 per month (includes 5g access)
Might wait until the release of the SE2 to see if JB will offer a decent Telstra deal.