IOS 12.3.1 hotspot isue

See this for troubleshooting, If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

I just updated my iPhone to IOS 12.3.1 and other phones no longer see my hotspot. I have to turn the hotspot off and back on for it to show up as a hotspot on other phones. Not a one and done, every couple of minutes. Very frustrating, I hope others will report this issue if seeing/having same issue.

Same happened to my iphone XR: I can't share mobile data with my macbook anymore. I have tried the troubleshooting mentioned above. It didn't work. I even changed the mobile providers but it didn't work either. Having this problem for more than 2 weeks. Is apple going to solve this?

"im using ios 13 beta 4"

So you are saying that this statement from you does not say that you are using beta software?

If you want ask someone to test something, like the first part of your statement, then leave off the other part. Any mention of beta software in a thread can get it removed and can also result in your being removed from the beta program. You signed an NDA not to discuss beta on a public forum. Just pay attention to what you are doing. While may have a problem with Hotspot, it is not a system wide issue, and expecting something from another version of software is not always the best thing. You have just as much opportunity to test iOS 12.4 as anyone, without having to use beta.

got bug on 12.3.1 can’t using personal hotspot after update i using iphone xr

Discussion of beta software is prohibited in the public forum. It is a violation of the NDA you signed to be part of the beta.

Then you should have left off the second line.