The recent unc0ver jailbreak release provides support for A12-A13 devices on iOS 13.0-13.3. However, please note that this Jailbreak is not fully stable yet.
IF YOUR DEVICE IS BELOW A12, USE CHECKRA1N.
For A12-A13 there's no substitute support. Some tweaks might work, but most will not. Please don't ask us for substitute support as it simply won't be provided until further notice.